Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/cffconvert.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out a copy of the repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Check whether the citation metadata from CITATION.cff is valid
         uses: citation-file-format/[email protected]

.github/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
   package:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
           fetch-tags: true

.github/workflows/unit_tests.yml

@@ -21,7 +21,7 @@ jobs:
       matrix:
         python-version: ["3.13"]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         fetch-tags: true
@@ -69,7 +69,7 @@ jobs:
         pip check
         python -m pip install build twine
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         fetch-tags: true
@@ -88,7 +88,7 @@ jobs:
     - name: Remove sdist install
       run: python -m pip uninstall -y mne-bids
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         fetch-tags: true
@@ -107,7 +107,7 @@ jobs:
     - name: Remove wheel install
       run: python -m pip uninstall -y mne-bids
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         fetch-tags: true
@@ -186,7 +186,7 @@ jobs:
       TZ: Europe/Berlin
       FORCE_COLOR: true
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         fetch-tags: true
@@ -337,7 +337,7 @@ jobs:
       matrix:
         python-version: ["3.13"]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         fetch-tags: true