Bump actions/checkout from 2 to 4 (#278)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/docs.yml

@@ -28,7 +28,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y libsnappy-dev libzzip-dev zlib1g-dev libboost-all-dev doxygen
       - name: checkout from git
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
         # re-use the cache from the linux build
       - name: ccache

.github/workflows/keyvi.yml

@@ -33,7 +33,7 @@ jobs:
           brew update
           brew install zlib snappy boost
       - name: checkout from git
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: ccache
         uses: hendrikmuhs/[email protected]

.github/workflows/rust.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Install system packages
       run: |
         sudo apt-get update

.github/workflows/style.yml

@@ -18,7 +18,7 @@ jobs:
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # fetch all history so multiple commits can be scanned
       - name: install deps