do not package app/models/content_search

There is no such directory.
addressing:
```
Processing files: katello-1.3.14-1.git.1285.c5ac5f2.el6.noarch
error: File not found: /builddir/build/BUILDROOT/katello-1.3.14-1.git.1285.c5ac5f2.el6.noarch/usr/share/katello/app/models/content_search
```
@jlsherrill Did you forgot in #1840 commit some directory or you add this line to spec by error?