CI: remove aarch64-macos runner for now

@github fucked me over and deleted the aarch64-macos runner's configuration
after it was down for a brief period of time[0] so I will have to set it up
from scratch again. For now, we remove aarch64-macos so our CI at least
passes once again.

[0] https://github.com/actions/runner/issues/756

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

.github/workflows/m1_ci.yml

@@ -1,31 +0,0 @@
-name: CI
-on:
-  # SECURITY: This must be a push event only, otherwise our M1 mac runner would be compromised by
-  # third-party pull requests which could run arbitrary code. This way, we can restrict it to
-  # collaborators of the repository only.
-  #
-  # Whenever GitHub Actions gets official M1 support, we can use that for PRs and get rid of this
-  # self-hosted runner: https://github.com/actions/virtual-environments/issues/2187
-  push:     
-    paths-ignore:
-      - "doc/**"
-      - "README.md"
-      - "**.md"
-      - "LICENSE**"
-jobs:
-  aarch64-macos:
-    if: ${{ github.repository == 'hexops/mach' }}
-    runs-on: [self-hosted, macOS, ARM64]
-    defaults:
-      run:
-        shell: '/usr/bin/arch -arch arm64e /bin/bash --noprofile --norc -eo pipefail {0}'
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-      - name: test
-        run: zig build test
-      - name: build
-        run: zig build
-      # TODO: get WASM builds working
-      # - name: build (WASM)
-      #   run: zig build -Dtarget=wasm32-freestanding-none