CI: do not install Zig on self-hosted runners (now managed by Wrench)

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

libs/gpu-dawn/.github/workflows/m1_ci.yml

@@ -18,10 +18,6 @@ jobs:
           rm -rf $GITHUB_WORKSPACE && mkdir $GITHUB_WORKSPACE
       - name: Checkout
         uses: actions/checkout@v2
-      - name: Setup Zig
-        run: |
-          sudo rm -rf /usr/local/bin/zig /usr/local/bin/lib/
-          sudo sh -c 'wget -c https://ziglang.org/builds/zig-macos-aarch64-0.11.0-dev.944+a193ec432.tar.xz -O - | tar -xJ --strip-components=1 -C /usr/local/bin'
       - name: Clone mach-glfw
         run: rm libs/mach-glfw && git clone https://github.com/hexops/mach-glfw libs/mach-glfw
       - name: install (debug)