Remove '.min' from asset when locating bp-legacy assets.

This ensures that the assets can be located when running from /src/ when the
minified files have not been built.

Props nofearinc.
Fixes #5963.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@9092 cdf35c40-ae34-48e0-9cc9-0c9da1808c22