Try fixing mambaforge miniforge mamba CI setup issue.

See conda-incubator/setup-miniconda#274

.github/workflows/ci.yaml

@@ -131,6 +131,7 @@ jobs:
           # see https://github.com/conda-incubator/setup-miniconda/issues/274#issue-1531425010
           # If that changes again in the future, also change it below in the other jobs.
           miniforge-variant: Mambaforge
+          miniforge-version: latest
           environment-file: envs/grenepipe.yaml
           activate-environment: grenepipe
 
@@ -213,6 +214,7 @@ jobs:
           # mamba-version: "*"
           # Need to use a different setup to get mamba to work, see above.
           miniforge-variant: Mambaforge
+          miniforge-version: latest
           environment-file: envs/grenepipe.yaml
           activate-environment: grenepipe
 
@@ -277,6 +279,7 @@ jobs:
           # mamba-version: "*"
           # Need to use a different setup now to get mamba to work, see above.
           miniforge-variant: Mambaforge
+          miniforge-version: latest
           environment-file: envs/grenepipe.yaml
           activate-environment: grenepipe