Revert "ci: add a problem matcher for GitHub Actions"

This reverts commit 676eb0c;
as we will be reverting the change to show these extra output
tokens under bash, the pattern would not match anything.

Helped-by: Carlo Marcelo Arenas Belón <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

ci/git-problem-matcher.json

@@ -157,11 +157,6 @@ then
 	MAKEFLAGS="$MAKEFLAGS --jobs=10"
 	test windows != "$CI_OS_NAME" ||
 	GIT_TEST_OPTS="--no-chain-lint --no-bin-wrappers $GIT_TEST_OPTS"
-
-	# https://github.com/actions/toolkit/blob/master/docs/commands.md#problem-matchers
-	echo "::add-matcher::ci/git-problem-matcher.json"
-	test linux-musl = "$jobname" ||
-	MAKEFLAGS="$MAKEFLAGS TEST_SHELL_PATH=/bin/sh"
 else
 	echo "Could not identify CI type" >&2
 	env >&2