t9902: fix 'test A == B' to use = operator

The == operator as an alias to = is not POSIX.  This doesn't actually
matter for the execution of the script, because it only runs when the
shell is bash.  However, it trips up test-lint, so it's nicer to use
the standard form.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9902-completion.sh

@@ -69,7 +69,7 @@ run_completion ()
 	local -a COMPREPLY _words
 	local _cword
 	_words=( $1 )
-	test "${1: -1}" == ' ' && _words+=('')
+	test "${1: -1}" = ' ' && _words+=('')
 	(( _cword = ${#_words[@]} - 1 ))
 	__git_wrap__git_main && print_comp
 }