[SPARK-14402][HOTFIX] Fix ExpressionDescription annotation

## What changes were proposed in this pull request?

Fix for the error introduced in https://github.com/apache/spark/commit/c59abad052b7beec4ef550049413e95578e545be:

```
/Users/jacek/dev/oss/spark/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala:626: error: annotation argument needs to be a constant; found: "_FUNC_(str) - ".+("Returns str, with the first letter of each word in uppercase, all other letters in ").+("lowercase. Words are delimited by white space.")
    "Returns str, with the first letter of each word in uppercase, all other letters in " +
                                                                                          ^
```

## How was this patch tested?

Local build

Author: Jacek Laskowski <jacek@japila.pl>

Closes #12192 from jaceklaskowski/SPARK-14402-HOTFIX.

0 files changed, 0 insertions, 0 deletions