[SPARK-3359][DOCS] Make javadoc8 working for unidoc/genjavadoc compatibility in Java API documentation

## What changes were proposed in this pull request?

This PR make `sbt unidoc` complete with Java 8.

This PR roughly includes several fixes as below:

- Fix unrecognisable class and method links in javadoc by changing it from `[[..]]` to `` `...` ``

  ```diff
  - * A column that will be computed based on the data in a [[DataFrame]].
  + * A column that will be computed based on the data in a `DataFrame`.
  ```

- Fix throws annotations so that they are recognisable in javadoc

- Fix URL links to `<a href="http..."></a>`.

  ```diff
  - * [[http://en.wikipedia.org/wiki/Decision_tree_learning Decision tree]] model for regression.
  + * <a href="http://en.wikipedia.org/wiki/Decision_tree_learning">
  + * Decision tree (Wikipedia)</a> model for regression.
  ```

  ```diff
  -   * see http://en.wikipedia.org/wiki/Receiver_operating_characteristic
  +   * see <a href="http://en.wikipedia.org/wiki/Receiver_operating_characteristic">
  +   * Receiver operating characteristic (Wikipedia)</a>
  ```

- Fix < to > to

  - `greater than`/`greater than or equal to` or `less than`/`less than or equal to` where applicable.

  - Wrap it with `{{{...}}}` to print them in javadoc or use `{code ...}` or `{literal ..}`. Please refer https://github.com/apache/spark/pull/16013#discussion_r89665558

- Fix `</p>` complaint

## How was this patch tested?

Manually tested by `jekyll build` with Java 7 and 8

```
java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)
```

```
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)
```

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16013 from HyukjinKwon/SPARK-3359-errors-more.

3 files changed, 12 insertions, 4 deletions

diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala
index a2d64da001..5f5c8e2432 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala
@@ -57,9 +57,17 @@ import org.apache.spark.util.SerializableJobConf
  * @param partition a map from the partition key to the partition value (optional). If the partition
  *                  value is optional, dynamic partition insert will be performed.
  *                  As an example, `INSERT INTO tbl PARTITION (a=1, b=2) AS ...` would have
- *                  Map('a' -> Some('1'), 'b' -> Some('2')),
+ *
+ *                  {{{
+ *                  Map('a' -> Some('1'), 'b' -> Some('2'))
+ *                  }}}
+ *
  *                  and `INSERT INTO tbl PARTITION (a=1, b) AS ...`
- *                  would have Map('a' -> Some('1'), 'b' -> None).
+ *                  would have
+ *
+ *                  {{{
+ *                  Map('a' -> Some('1'), 'b' -> None)
+ *                  }}}.
  * @param child the logical plan representing data to write to.
  * @param overwrite overwrite existing table or partitions.
  * @param ifNotExists If true, only write if the table or partition does not exist.
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala
index 32edd4aec2..90e86959cd 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala
@@ -177,7 +177,7 @@ private[hive] case class HiveGenericUDF(
 
 /**
  * Converts a Hive Generic User Defined Table Generating Function (UDTF) to a
- * [[Generator]].  Note that the semantics of Generators do not allow
+ * `Generator`. Note that the semantics of Generators do not allow
  * Generators to maintain state in between input rows.  Thus UDTFs that rely on partitioning
  * dependent operations like calls to `close()` before producing output will not operate the same as
  * in Hive.  However, in practice this should not affect compatibility for most sane UDTFs
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveWriterContainers.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveWriterContainers.scala
index a34e2e76f5..0c9321068c 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveWriterContainers.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveWriterContainers.scala
@@ -49,7 +49,7 @@ import org.apache.spark.util.collection.unsafe.sort.UnsafeExternalSorter
 
 /**
  * Internal helper class that saves an RDD using a Hive OutputFormat.
- * It is based on [[SparkHadoopWriter]].
+ * It is based on `SparkHadoopWriter`.
  */
 private[hive] class SparkHiveWriterContainer(
     @transient private val jobConf: JobConf,