CI: cargo clean before tests

As of now, the CI doesn't pass simply because of no space
left on the device to proceed with the compilation of the tests.

In this commit we execute `cargo clean` before compilation and execution
of the tests.

.github/workflows/rust.yml

@@ -51,7 +51,9 @@ jobs:
     - name: Build
       run: cargo build --verbose --all-targets --features "full-serialization"
     - name: Run tests
-      run: SCYLLA_URI=172.42.0.2:9042 SCYLLA_URI2=172.42.0.3:9042 SCYLLA_URI3=172.42.0.4:9042 cargo test --verbose --features "full-serialization"
+      run: |
+        cargo clean
+        SCYLLA_URI=172.42.0.2:9042 SCYLLA_URI2=172.42.0.3:9042 SCYLLA_URI3=172.42.0.4:9042 cargo test --verbose --features "full-serialization"
     - name: Stop the cluster
       if: ${{ always() }}
       run: docker compose -f test/cluster/docker-compose.yml stop