Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/backend-tests.yml

@@ -22,7 +22,7 @@ jobs:
           version: 1.0
       -
         name: Install etherpad core
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: ether/etherpad-lite
           path: etherpad-lite
@@ -44,7 +44,7 @@ jobs:
             ${{ runner.os }}-pnpm-store-
       -
         name: Checkout plugin repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: plugin
       -

.github/workflows/frontend-tests.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       -
         name: Check out Etherpad core
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: ether/etherpad-lite
       - uses: pnpm/action-setup@v3
@@ -33,7 +33,7 @@ jobs:
             ${{ runner.os }}-pnpm-store-
       -
         name: Check out the plugin
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: ./node_modules/__tmp
       -

.github/workflows/npmpublish.yml

@@ -15,7 +15,7 @@ jobs:
           node-version: 20
           registry-url: https://registry.npmjs.org/
       - name: Check out Etherpad core
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: ether/etherpad-lite
       - uses: pnpm/action-setup@v3
@@ -35,7 +35,7 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-pnpm-store-
       -
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       -