ci: use mlugg's zig action

Author: nektro

.github/workflows/nightly.yml

@@ -24,8 +24,9 @@ jobs:
           submodules: "recursive"
 
       - name: Setup Zig
-        uses: goto-bus-stop/setup-zig@v2
+        uses: mlugg/setup-zig@v1
         with:
+          mirror: "http://mirrors.nektro.net/s3cgi"
           version: "0.12.0"
 
       - run: zig version

.github/workflows/push.yml

@@ -17,8 +17,9 @@ jobs:
       - run: top -b -n 1 | head -n5
 
       - name: Setup Zig
-        uses: goto-bus-stop/setup-zig@v2
+        uses: mlugg/setup-zig@v1
         with:
+          mirror: "http://mirrors.nektro.net/s3cgi"
           version: "0.12.0"
 
       - run: zig version