Removed deprecated --enable-test-discovery flag

Author: dimitribouniol

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
       uses: actions/checkout@v2
     - name: Build
       run: |
-        swift build --build-tests --enable-test-discovery --enable-index-store --configuration release  -Xswiftc -warnings-as-errors -Xcc -Werror
+        swift build --build-tests --enable-index-store --configuration release -Xswiftc -warnings-as-errors -Xcc -Werror
     - name: Run Tests
       run: |
-        swift test --skip-build --enable-test-discovery --enable-index-store --configuration release
+        swift test --skip-build --enable-index-store --configuration release