ci: update to upload-artifact v4

v3 has been deprecated, see: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

Author: Austinpayne

.github/workflows/build.yml

@@ -51,7 +51,7 @@ jobs:
           --format html \
           --output-dir=.test-coverage
     - name: Upload test coverage html
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: test-coverage-report
         path: .test-coverage
@@ -68,4 +68,4 @@ jobs:
         swift-version: ${{ matrix.swift }}
     - uses: actions/checkout@v3
     - name: Test
-      run: swift test --parallel
+      run: swift test --parallel