Bump actions/checkout from 6 to 7 (#368)

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  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>

.github/workflows/check_links.yml

@@ -28,7 +28,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       # Restore cache
       - name: Restore lychee cache

.github/workflows/update_links.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Query Scryfall API and update picURLs
         shell: bash

.github/workflows/update_version.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Get previous version
         id: get_versions