Only run Zarr v2 CI tests on default local executors (#759)

Don't run on Lithops in CI as it is flaky, which might mask any failures
due to Zarr v2/v3 differences

Author: tomwhite

.github/workflows/zarr-v2-tests.yml

@@ -43,7 +43,7 @@ jobs:
 
       - name: Install
         run: |
-          python -m pip install -e .[test,lithops]
+          python -m pip install -e .[test]
           python -m pip install -U 'zarr<3'
 
       - name: Run tests