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>

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
         scalaversion: ["2.11.12", "2.12.15", "2.13.6", "3.1.3"]
     steps:
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Scala
         uses: japgolly/setup-everything-scala@v3.1
@@ -34,7 +34,7 @@ jobs:
   readme:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: japgolly/setup-everything-scala@v3.1
       - name: Readme generation
         run: sbt readme/run

.github/workflows/ghpages.yml

@@ -10,7 +10,7 @@ jobs:
   build-and-deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Scala
         uses: japgolly/setup-everything-scala@v3.1

.github/workflows/release.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0