Followup to r1568571, fix grammar in comments.

* subversion/libsvn_wc/translate.c
  (svn_wc__internal_translated_streams): Remove extra if in comments.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1568573 13f79535-47bb-0310-9956-ffa450edef68