Corrected copy-and-paste thinko in ignore executable bit test case.

This test should be testing update-index --add, not git-add as the
latter is implemented in terms of the former.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

t/t3700-add.sh

@@ -35,7 +35,7 @@ test_expect_success \
 	'git repo-config core.filemode 0 &&
 	 echo foo >xfoo2 &&
 	 chmod 755 xfoo2 &&
-	 git-add xfoo2 &&
+	 git-update-index --add xfoo2 &&
 	 case "`git-ls-files --stage xfoo2`" in
 	 100644" "*xfoo2) echo ok;;
 	 *) echo fail; git-ls-files --stage xfoo2; exit 1;;