chore(deps): bump actions/checkout from 3 to 6 (#238)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
     timeout-minutes: 5
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Download addlicense
         run: |
@@ -67,7 +67,7 @@ jobs:
         working-directory: packages/firebase_admin_sdk
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: dart-lang/setup-dart@v1
         with:
@@ -114,7 +114,7 @@ jobs:
         working-directory: packages/firebase_admin_sdk
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
@@ -250,7 +250,7 @@ jobs:
         working-directory: packages/firebase_admin_sdk
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
@@ -304,7 +304,7 @@ jobs:
         working-directory: packages/firebase_admin_sdk
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: dart-lang/setup-dart@v1
         with:

.github/workflows/docs.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
 
       - uses: dart-lang/setup-dart@v1
         with: