cicd: update Zig version to 0.15.1

Author: Ryoga-exe

.github/workflows/docs.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Setup Zig
         uses: mlugg/setup-zig@v2
         with:
-          version: 0.14.1
+          version: 0.15.1
       - name: Build docs
         run: zig build docs
       - name: Upload artifact