Run memory utilization tests on Zarr Python v3 only

Author: tomwhite

.github/workflows/slow-tests.yml

@@ -19,7 +19,6 @@ jobs:
       matrix:
         os: ["ubuntu-latest"]
         python-version: ["3.12"]
-        zarr: ["<3"]
 
     steps:
       - name: Checkout source
@@ -43,10 +42,6 @@ jobs:
         run: |
           python -m pip install -e .[test] memray
 
-      - name: Install zarr${{ matrix.zarr }}
-        run: |
-          python -m pip install -U 'zarr${{ matrix.zarr }}'
-
       - name: Run tests
         run: |
           pytest -vs -k slow --runslow