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/t7012-skip-worktree-writing.sh

@@ -134,21 +134,6 @@ test_expect_success 'git-clean, dirty case' '
 	test_i18ncmp expected result
 '
 
-test_expect_success '--ignore-skip-worktree-entries leaves worktree alone' '
-	test_commit keep-me &&
-	git update-index --skip-worktree keep-me.t &&
-	rm keep-me.t &&
-
-	: ignoring the worktree &&
-	git update-index --remove --ignore-skip-worktree-entries keep-me.t &&
-	git diff-index --cached --exit-code HEAD &&
-
-	: not ignoring the worktree, a deletion is staged &&
-	git update-index --remove keep-me.t &&
-	test_must_fail git diff-index --cached --exit-code HEAD \
-		--diff-filter=D -- keep-me.t
-'
-
 #TODO test_expect_failure 'git-apply adds file' false
 #TODO test_expect_failure 'git-apply updates file' false
 #TODO test_expect_failure 'git-apply removes file' false