Remove activity comment count check in activity entry template.

Due to changes in r6410 to expand how activity comments are fetched, a
comment count now existed for nested activity comments.

Because the comment count now exists for nested activity comments, this had
the unintended consequence of showing activity comments on singular
activity comment entries.  Since the current javascript / AJAX code is
unable to determine the parent activity ID correctly on a singular
activity comment item, this would result in the "View Conversation" link
being incorrect for replies that were made to these items.

This commit resolves this issue by removing the activity comment count
check, which will not output the activity comment form for singular
activity comment entries.

Fixes #5172.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7482 cdf35c40-ae34-48e0-9cc9-0c9da1808c22