Activate try-gmt environment in setup-miniconda step

Author: weiji14

.github/workflows/repo2docker.yml

@@ -17,8 +17,10 @@ jobs:
       - name: Setup Miniconda
         uses: conda-incubator/setup-miniconda@835234971496cad1653abb28a638a281cf32541f # v3.2.0
         with:
+          activate-environment: try-gmt
           conda-remove-defaults: "true"
           conda-solver: libmamba
+          environment-file: environment.yml
           miniforge-version: latest
 
       - name: Install dependencies