Trying to fix flakyness by making hub_2 and hub_3 serial tests (potential issue on mingw with mmap).

.github/workflows/rust-ci.yml

@@ -40,8 +40,6 @@ jobs:
           profile: minimal
           toolchain: ${{ matrix.rust }}
           override: true
-      - name: Setup tmate session
-        uses: mxschmitt/action-tmate@v3
       - uses: actions-rs/cargo@v1
         with:
           command: test