Bump actions/cache from 3 to 4 (#400)

Bumps [actions/cache](https://github.com/actions/cache) from 3 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  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/build-docs.yml

@@ -45,7 +45,7 @@ jobs:
         shell: bash
 
       - name: Restore LFS cache (private repository)
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: lfs-cache
         with:
           path: ./traffic_data/.git/lfs
@@ -61,7 +61,7 @@ jobs:
 
       # virtualenv cache should depends on OS, Python version and `poetry.lock` (and optionally workflow files).
       - name: Cache Packages
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.local
@@ -79,7 +79,7 @@ jobs:
         run: poetry run python -c "import sys; print(sys.version)"
 
       - name: Cache folder for traffic
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache-folder
         with:
           path: |
@@ -89,7 +89,7 @@ jobs:
           key: traffic-${{ runner.os }}
 
       - name: Cache folder for documentation
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: docs-folder
         with:
           path: |

.github/workflows/run-tests.yml

@@ -54,7 +54,7 @@ jobs:
         shell: bash
 
       - name: Restore LFS cache (private repository)
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: lfs-cache
         with:
           path: ./traffic_data/.git/lfs
@@ -70,7 +70,7 @@ jobs:
 
       # virtualenv cache should depends on OS, Python version and `poetry.lock` (and optionally workflow files).
       - name: Cache Packages
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.local
@@ -88,7 +88,7 @@ jobs:
         run: poetry run python -c "import sys; print(sys.version)"
 
       - name: Cache folder for traffic
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache-folder
         with:
           path: |