chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/check_build.yaml

@@ -6,5 +6,5 @@ jobs:
   build_and_deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - run: yarn install && yarn build

.github/workflows/firebase-hosting-merge.yml

@@ -10,7 +10,7 @@ jobs:
   build_and_deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - run: yarn install && yarn build
       - uses: FirebaseExtended/action-hosting-deploy@v0
         with: