[Local Branch Indicator] Change case from No upstream to no upstream

This commit fixes the Local Indicator which was broken because of theme related changes.

gitstatus.sh

@@ -78,7 +78,7 @@ else
   # detect if the local branch have a remote tracking branch
   cmd_output=$(git rev-parse --abbrev-ref ${branch}@{upstream} 2>&1 >/dev/null)
 
-  if [ `count_lines "$cmd_output" "fatal: No upstream"` == 1 ] ; then
+  if [ `count_lines "$cmd_output" "fatal: no upstream"` == 1 ] ; then
     has_remote_tracking=0
   else
     has_remote_tracking=1