receive.fsck.<msg-id> tests: remove dead code

Remove the setting of a receive.fsck.badDate config variable to
"ignore". This was added in efaba7c ("fsck: optionally ignore
specific fsck issues completely", 2015-06-22) but never did anything,
presumably it was part of some work-in-progress code that never made
it into git.git.

None of these tests will emit the "invalid author/committer line - bad
date" warning. The dates on the commit objects we're setting up are
not invalid.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5504-fetch-receive-strict.sh

@@ -149,8 +149,6 @@ test_expect_success 'push with receive.fsck.missingEmail=warn' '
 	git --git-dir=dst/.git branch -D bogus &&
 	git --git-dir=dst/.git config --add \
 		receive.fsck.missingEmail ignore &&
-	git --git-dir=dst/.git config --add \
-		receive.fsck.badDate warn &&
 	git push --porcelain dst bogus >act 2>&1 &&
 	! grep "missingEmail" act
 '