tests: fix mambaforge installer doesn't exist anymore

Author: epruesse

.github/workflows/release.yml

@@ -28,7 +28,6 @@ jobs:
           fetch-depth: 0  # full history for setuptools_scm
       - uses: conda-incubator/setup-miniconda@v3
         with:
-          miniforge-variant: Mambaforge
           mamba-version: "*"
           use-mamba: true
           channels: conda-forge,bioconda

.github/workflows/tests.yml

@@ -26,7 +26,6 @@ jobs:
           fetch-depth: 0  # full history for setuptools_scm
       - uses: conda-incubator/setup-miniconda@v3
         with:
-          miniforge-variant: Mambaforge
           mamba-version: "*"
           use-mamba: true
           channels: conda-forge,bioconda