Fix pcodec install

Author: dstansby

.github/workflows/ci.yaml

@@ -68,7 +68,7 @@ jobs:
         shell: "bash -l {0}"
         run: |
             conda activate env
-            python -m pip install -v pcodec
+            python -m pip install -v ".[pcodec]"
 
 
       # This is used to test with zfpy, which does not yet support numpy 2.0