Update action versions and use ubuntu-slim where applicable

.github/workflows/CI.yml

@@ -24,7 +24,7 @@ jobs:
       # the order of the checkout actions is important because all contents of
       # the target folder of the checkout action is removed
       - name: "Clone the package"
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: ${{ matrix.package }}
 
@@ -36,7 +36,7 @@ jobs:
           sed -i -E "s|(Date[[:space:]]*:?=[[:space:]]*['\"]).*(['\"])|\1${DATE}\2|" "PackageInfo.g"
 
       - name: "Check out this repository"
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           path: .this-action/
 
@@ -56,12 +56,12 @@ jobs:
 
   test-scripts:
     name: "Test the scripts used by this action"
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
 
     steps:
 
       - name: "Check out this repository"
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: "Shellcheck"
         shell: bash

README.md

@@ -85,7 +85,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: gap-actions/setup-gap@v3
       - uses: gap-actions/build-pkg-docs@v2
         with:

action.yml

@@ -227,7 +227,7 @@ runs:
         target_commitish: ${{ github.sha }}
 
     - name: "Upload the release"
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       if: ${{ inputs.dry-run == 'true' }}
       with:
         name: "Release_for_${{ env.PKGNAME }}_${{ env.VERSION }}"