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] <support@github.com>

Author: dependabot[bot]

.github/workflows/R-CMD-check-wsl.yaml

@@ -35,7 +35,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
         if: "!startsWith(github.ref, 'refs/tags/') && github.ref != 'refs/heads/master'"
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-r@v2.6.4
         with:

.github/workflows/R-CMD-check.yaml

@@ -48,7 +48,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
         if: "!startsWith(github.ref, 'refs/tags/') && github.ref != 'refs/heads/master'"
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install system dependencies
         if: runner.os == 'Linux'

.github/workflows/Test-coverage.yaml

@@ -32,7 +32,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           workflow: Test-coverage.yml
         if: "!startsWith(github.ref, 'refs/tags/') && github.ref != 'refs/heads/master'"
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-r@v2.6.4
       - uses: r-lib/actions/setup-pandoc@v2.6.4
@@ -83,7 +83,7 @@ jobs:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
       NOT_CRAN: true
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-r@v2.6.4
         with:

.github/workflows/cmdstan-tarball-check.yaml

@@ -32,7 +32,7 @@ jobs:
       NOT_CRAN: true
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install system dependencies
         if: runner.os == 'Linux'
         run: |