Update actions/cache to V4.

The latest version should work around a NodeJS 20 issue related to
keep-alive for which caching always takes 2 minutes.

.github/actions/poetry_setup/action.yml

@@ -28,7 +28,7 @@ runs:
       with:
         python-version: ${{ inputs.python-version }}
 
-    - uses: actions/cache@v3
+    - uses: actions/cache@v4
       id: cache-bin-poetry
       name: Cache Poetry binary - Python ${{ inputs.python-version }}
       env:
@@ -51,7 +51,7 @@ runs:
         # Refresh the shell hashtable, to ensure correct `which` output.
         hash -r
 
-        # `actions/cache@v3` doesn't always seem able to correctly unpack softlinks.
+        # `actions/cache@v4` doesn't always seem able to correctly unpack softlinks.
         # Delete and recreate the softlinks pipx expects to have.
         rm /opt/pipx/venvs/poetry/bin/python
         cd /opt/pipx/venvs/poetry/bin
@@ -75,7 +75,7 @@ runs:
       run: pipx install "poetry==$POETRY_VERSION" --python '${{ steps.setup-python.outputs.python-path }}' --verbose
 
     - name: Restore pip and poetry cached dependencies
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       env:
         SEGMENT_DOWNLOAD_TIMEOUT_MIN: "4"
       with:

.github/workflows/_lint.yml

@@ -61,7 +61,7 @@ jobs:
 
       - name: Get .mypy_cache to speed up mypy
         if: steps.changed-files.outputs.all
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           SEGMENT_DOWNLOAD_TIMEOUT_MIN: "2"
         with:
@@ -94,7 +94,7 @@ jobs:
 
       - name: Get .mypy_cache_test to speed up mypy
         if: steps.changed-files.outputs.all
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           SEGMENT_DOWNLOAD_TIMEOUT_MIN: "2"
         with: