ci(github): Update GitHub Actions to use immutable flag for Yarn

--frozen-lockfile option is deprecated

Author: PresentKim

.github/workflows/deploy-github-pages.yml

@@ -16,7 +16,7 @@ jobs:
           cache: yarn
 
       - name: Install dependencies
-        run: yarn install --frozen-lockfile
+        run: yarn install --immutable
 
       - name: Build project
         env: