t0300: don't create unused file

Test 'credential config with partial URLs' in t0300-credentials.sh
contains three "git credential fill" invocations.  For two of the
invocations, the test asserts presence or absence of string "yep" in the
standard output.  For the third test it checks for an error message in
standard error.

Don't redirect standard output of "git credential" to file "stdout" in
t0300-credentials.sh to avoid creating an unnecessary file when only
standard error is checked.

Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0300-credentials.sh

@@ -808,7 +808,7 @@ test_expect_success 'credential config with partial URLs' '
 
 	git -c credential.$partial.helper=yep \
 		-c credential.with%0anewline.username=uh-oh \
-		credential fill <stdin >stdout 2>stderr &&
+		credential fill <stdin 2>stderr &&
 	test_i18ngrep "skipping credential lookup for key" stderr
 '