t0301: another fix for Windows compatibility

Just like 0fdcfa2f9f5 (t0301: fixes for windows compatibility,
2021-09-14) explained, we should not call `mkdir -m<mode>` in the test
suite because that would fail on Windows.

There was one forgotten instance of this which was hidden by a `SYMLINK`
prerequisite. Currently, this prevents this test case from being
executed on Windows, but with the upcoming support for symbolic links,
it would become a problem.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0301-credential-cache.sh

diff --git a/t/t0301-credential-cache.sh b/t/t0301-credential-cache.sh
index dc30289..6f7cfd9 100755
--- a/t/t0301-credential-cache.sh
+++ b/t/t0301-credential-cache.sh
@@ -123,7 +123,8 @@
 		rmdir \"\$HOME/dir/\" &&
 		rm \"\$HOME/.git-credential-cache\"
 	" &&
-	mkdir -p -m 700 "$HOME/dir/" &&
+	mkdir -p "$HOME/dir/" &&
+	chmod 700 "$HOME/dir/" &&
 	ln -s "$HOME/dir" "$HOME/.git-credential-cache" &&
 	check approve cache <<-\EOF &&
 	protocol=https