Docstring fixes. No functional change.

* subversion/tests/libsvn_fs_fs/fs-fs-pack-test.c
  (): Fix file docstring.

* subversion/tests/libsvn_fs_x/fs-x-pack-test.c
  (): Same.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1622943 13f79535-47bb-0310-9956-ffa450edef68