t3301-notes: insert a shbang line in ./fake_editor.sh

This is required on Windows because git-notes is now a built-in
rather than a shell script.
Signed-off-by: NJohannes Sixt <j6t@kdbg.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t3301-notes.sh

@@ -8,6 +8,7 @@ test_description='Test commit notes'
 . ./test-lib.sh
 
 cat > fake_editor.sh << \EOF
+#!/bin/sh
 echo "$MSG" > "$1"
 echo "$MSG" >& 2
 EOF