Blogs: When recording a comment and looking for the blog post activity item, do not add a check for the user ID.

Adding a check for the user ID is not needed and would be inaccurate
since a commenter's user ID will not be the same as the post author's.
When the user IDs do not match, the associated activity comment is not
created.

See #5130, #5507

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8228 cdf35c40-ae34-48e0-9cc9-0c9da1808c22