Revert "create-pull-request: Fix error on 2.0 versions of git"

This breaks create-pull-request for git <2, which is many people.

This reverts commit 7ee64ea60ede5477b2f9a355d93bdc556e6b7895.

(From OE-Core rev: 26766ea8ee0ef121e54ff9084c4637aa8df984f4)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/create-pull-request

@@ -125,10 +125,6 @@ if [ -z "$BRANCH" ]; then
 	echo "NOTE: Assuming remote branch '$BRANCH', use -b to override."
 fi
 
-if [ "$COMMIT_ID" == "HEAD" ]; then
-	COMMIT_ID="$BRANCH"
-fi
-
 if [ -z "$REMOTE_URL" ]; then
 	echo "ERROR: Missing parameter -u, no git remote!"
 	usage