revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/t/t0050-filesystem.sh

@@ -131,24 +131,4 @@ $test_unicode 'merge (silent unicode normalization)' '
 	git merge topic
 '
 
-test_expect_success CASE_INSENSITIVE_FS 'checkout with no pathspec and a case insensitive fs' '
-	git init repo &&
-	(
-		cd repo &&
-
-		>Gitweb &&
-		git add Gitweb &&
-		git commit -m "add Gitweb" &&
-
-		git checkout --orphan todo &&
-		git reset --hard &&
-		mkdir -p gitweb/subdir &&
-		>gitweb/subdir/file &&
-		git add gitweb &&
-		git commit -m "add gitweb/subdir/file" &&
-
-		git checkout master
-	)
-'
-
 test_done