tools: only use 2 cores for macos action

There are only 2 cores available so we shouldn't be using -j8

Refs: https://docs.github.com/en/free-pro-team@latest/actions/reference/specifications-for-github-hosted-runners#supported-runners-and-hardware-resources

PR-URL: #36169
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Mary Marchini <oss@mmarchini.me>

.github/workflows/test-macos.yml

@@ -25,6 +25,6 @@ jobs:
       - name: Environment Information
         run: npx envinfo
       - name: Build
-        run: make build-ci -j8 V=1 CONFIG_FLAGS="--error-on-warn --experimental-quic"
+        run: make build-ci -j2 V=1 CONFIG_FLAGS="--error-on-warn --experimental-quic"
       - name: Test
-        run: make run-ci -j8 V=1 TEST_CI_ARGS="-p actions"
+        run: make run-ci -j2 V=1 TEST_CI_ARGS="-p actions"