Fix CI failures due to deprecation

Author: T-Nicholls

.github/actions/install_requirements/action.yml

@@ -36,7 +36,7 @@ runs:
       shell: bash
 
     - name: Upload lockfiles
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: lockfiles
         path: lockfiles

.github/workflows/code.yml

@@ -88,7 +88,7 @@ jobs:
           pipx run build
 
       - name: Upload sdist and wheel as artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: dist
           path: dist
@@ -124,7 +124,7 @@ jobs:
         run: echo IMAGE_REPOSITORY=ghcr.io/$(tr '[:upper:]' '[:lower:]' <<< "${{ github.repository }}") >> $GITHUB_ENV
 
       - name: Download wheel and lockfiles
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           path: artifacts/
 
@@ -177,7 +177,7 @@ jobs:
       HAS_PYPI_TOKEN: ${{ secrets.PYPI_TOKEN != '' }}
 
     steps:
-      - uses: actions/download-artifact@v3
+      - uses: actions/download-artifact@v4
 
       - name: Fixup blank lockfiles
         # Github release artifacts can't be blank