ci: replace mise action with direct pnpm install

.github/workflows/build.yml

@@ -16,10 +16,8 @@ jobs:
       - name: Checkout assets
         run: git -c submodule."assets".update=checkout submodule update --init assets
 
-      - name: Setup Mise
-        uses: immich-app/devtools/actions/use-mise@cd24790a7f5f6439ac32cc94f5523cb2de8bfa8c # use-mise-action-v1.1.0
-        with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Install pnpm
+        run: npm install -g pnpm@10.18.1
 
       - name: Install dependencies
         run: pnpm install