Remove Git ignore exclusion of .sha1 files

This exclusion could cause invalid .sha1 files to be left
in resources on the trybots instead of being wiped.

BUG=4267
TBR=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/39929004

Cr-Commit-Position: refs/heads/master@{#8327}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8327 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed