[MINOR][DOC] Fix style in examples across documentation

## What changes were proposed in this pull request?

This PR fixes the documentation as below:

  -  Python has 4 spaces and Java and Scala has 2 spaces (See https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide).

  - Avoid excessive parentheses and curly braces for anonymous functions. (See https://github.com/databricks/scala-style-guide#anonymous)

## How was this patch tested?

N/A

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #14593 from HyukjinKwon/minor-documentation.

1 files changed, 4 insertions, 4 deletions

diff --git a/docs/graphx-programming-guide.md b/docs/graphx-programming-guide.md
index bf4b968eb8..6f738f0599 100644
--- a/docs/graphx-programming-guide.md
+++ b/docs/graphx-programming-guide.md
@@ -421,15 +421,15 @@ val graph = Graph(users, relationships, defaultUser)
 // Notice that there is a user 0 (for which we have no information) connected to users
 // 4 (peter) and 5 (franklin).
 graph.triplets.map(
-    triplet => triplet.srcAttr._1 + " is the " + triplet.attr + " of " + triplet.dstAttr._1
-  ).collect.foreach(println(_))
+  triplet => triplet.srcAttr._1 + " is the " + triplet.attr + " of " + triplet.dstAttr._1
+).collect.foreach(println(_))
 // Remove missing vertices as well as the edges to connected to them
 val validGraph = graph.subgraph(vpred = (id, attr) => attr._2 != "Missing")
 // The valid subgraph will disconnect users 4 and 5 by removing user 0
 validGraph.vertices.collect.foreach(println(_))
 validGraph.triplets.map(
-    triplet => triplet.srcAttr._1 + " is the " + triplet.attr + " of " + triplet.dstAttr._1
-  ).collect.foreach(println(_))
+  triplet => triplet.srcAttr._1 + " is the " + triplet.attr + " of " + triplet.dstAttr._1
+).collect.foreach(println(_))
 {% endhighlight %}
 
 > Note in the above example only the vertex predicate is provided.  The `subgraph` operator defaults