Update GitHub actions to v4 (major) (#423)

* Update GitHub actions to v4

* revert codecov update

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Carl Csaposs <carl.csaposs@canonical.com>

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -24,7 +24,7 @@ jobs:
     timeout-minutes: 5
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Install tox & poetry
         run: |
           pipx install tox
@@ -40,7 +40,7 @@ jobs:
     timeout-minutes: 5
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - run: |

.github/workflows/release.yaml

@@ -23,7 +23,7 @@ jobs:
     timeout-minutes: 60
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - run: |

.github/workflows/sync_docs.yaml

@@ -16,7 +16,7 @@ jobs:
       contents: write  # Needed to login to Discourse
       pull-requests: write # Need to create PR
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Open PR with docs changes
         uses: deusebio/discourse-gatekeeper@c8adb89ea1cbceca54d78da798658373615487ac
         id: docs-pr