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

This reverts commit 676eb0c1ce0d380478eb16bdc5a3f2a7bc01c1d2;
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 <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/git-problem-matcher.json

@@ -1,16 +0,0 @@
-{
-    "problemMatcher": [
-        {
-            "owner": "git-test-suite",
-            "pattern": [
-                {
-                    "regexp": "^([^ :]+\\.sh):(\\d+): (error|warning|info):\\s+(.*)$",
-                    "file": 1,
-                    "line": 2,
-                    "severity": 3,
-                    "message": 4
-                }
-            ]
-        }
-    ]
-}

ci/lib.sh

@@ -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