[SPARK-15087][MINOR][DOC] Follow Up: Fix the Comments

## What changes were proposed in this pull request?
Remove the Comment, since it not longer applies. see the discussion here(https://github.com/apache/spark/pull/12865#discussion-diff-61946906)

Author: Sandeep Singh <sandeep@techaddict.me>

Closes #12953 from techaddict/SPARK-15087-FOLLOW-UP.