CI: update mlugg/setup-zig to v2

Author: leecannon

.github/workflows/CI.yml

@@ -23,9 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-
-      # FIXME: once https://github.com/mlugg/setup-zig/pull/30 is in a released version switch to that
-      - uses: mlugg/setup-zig@153c8d5202cbb8c7e10831110a3afd27593eb960
+      - uses: mlugg/setup-zig@v2
 
       - name: Lint
         run: zig fmt --check --ast-check .