Twenty Fourteen: fix comment for `twentyfourteen_excerpt_length()`, props SergeyBiryukov. Fixes #25297.

git-svn-id: https://develop.svn.wordpress.org/trunk@25406 602fd350-edb4-49c9-b593-d223f7449a82
Revert [25405] and use a file that does exist. see #25282.


git-svn-id: https://develop.svn.wordpress.org/trunk@25407 602fd350-edb4-49c9-b593-d223f7449a82