chore: bump actions/checkout from 6 to 7

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](actions/checkout@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>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -17,7 +17,7 @@ jobs:
     steps:
 
       - name: checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: build
         uses: leanprover/lean-action@v1

.github/workflows/publish.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
 
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Install Lean
         uses: leanprover/lean-action@v1

.github/workflows/push-to-nightly.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
 
       - name: checkout repo
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           ref: nightly-testing
           fetch-depth: 0

.github/workflows/release.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
 
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Install Lean
         uses: leanprover/lean-action@v1

.github/workflows/update-nightly-toolchain.yml

@@ -11,7 +11,7 @@ jobs:
     steps:
 
       - name: checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           ref: nightly-testing
           token: ${{ secrets.UNICODE_BASIC_TOKEN }}

.github/workflows/update-toolchain.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
 
       - name: checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           ref: nightly-testing
           fetch-depth: 0