ci: update mlugg/setup-zig

Author: kassane

.github/workflows/CI.yml

@@ -14,7 +14,7 @@ jobs:
         with:
           submodules: recursive
           fetch-depth: 0
-      - uses: mlugg/setup-zig@v1
+      - uses: mlugg/setup-zig@v2
 
       - name: Testing
         run: zig run runall.zig