vim syntax: follow recent changes to commit template

This patch changes the syntax highlighting to correctly match the new
text of the commit message introduced by
  82dca848Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

contrib/vim/syntax/gitcommit.vim

 syn region gitLine start=/^#/ end=/$/
-syn region gitCommit start=/^# Updated but not checked in:$/ end=/^#$/ contains=gitHead,gitCommitFile
+syn region gitCommit start=/^# Added but not yet committed:$/ end=/^#$/ contains=gitHead,gitCommitFile
 syn region gitHead contained start=/^#   (.*)/ end=/^#$/
-syn region gitChanged start=/^# Changed but not updated:/ end=/^#$/ contains=gitHead,gitChangedFile
+syn region gitChanged start=/^# Changed but not added:/ end=/^#$/ contains=gitHead,gitChangedFile
 syn region gitUntracked start=/^# Untracked files:/ end=/^#$/ contains=gitHead,gitUntrackedFile
 
 syn match gitCommitFile contained /^#\t.*/hs=s+2