CI: disable scipy.spatial from pytest-run-parallel job

Author: rgommers

.github/workflows/linux.yml

@@ -504,7 +504,9 @@ jobs:
     - name: Run tests (fast, with pytest-run-parallel)
       if: ${{ matrix.parallel == '1'}}
       env:
-        # scipy.special and scipy.stats are waiting on special.errstate being made thread-safe
+        # Excluded modules:
+        # - scipy.special and scipy.stats are waiting on special.errstate being made thread-safe
+        # - scipy.spatial has multiple issues  in kdtree/qhull, and gh-20655 is pending.
         TEST_SUBMODULES: >-
           -t scipy.cluster
           -t scipy.constants
@@ -522,7 +524,6 @@ jobs:
           -t scipy.optimize
           -t scipy.signal
           -t scipy.sparse
-          -t scipy.spatial
       run: |
         # Note: only fast tests; full test suite is unlikely to uncover anything more,
         #       and it'll be quite slow with pytest-run-parallel