chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/integrate.yaml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install dependencies
       run: |
         set -eux
@@ -32,7 +32,7 @@ jobs:
     name: Unit Tests
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install dependencies
         run: pip install tox
       - run: tox -vve unit
@@ -41,7 +41,7 @@ jobs:
     name: Integration Tests
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Setup operator environment
       uses: charmed-kubernetes/actions-operator@main
       with:

.github/workflows/publish.yaml

@@ -32,7 +32,7 @@ jobs:
     outputs:
       charm_paths_list: ${{ steps.get-charm-paths.outputs.CHARM_PATHS_LIST }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with: 
           fetch-depth: 0
           ref: ${{ inputs.source_branch }}
@@ -52,7 +52,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ inputs.source_branch }}

.github/workflows/release.yaml

@@ -16,7 +16,7 @@ jobs:
     name: Promote charm
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Release charm to channel
         uses: canonical/charming-actions/release-charm@2.4.0
         with: