Disable caching of conda packages

Use conda since it now runs libmamba. With the caching we couldn't the
latest GMT.

.github/workflows/docs.yml

@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       REQUIREMENTS: env/requirements-docs.txt env/requirements-build.txt
-      PYTHON: 3.9
+      PYTHON: 3.10
 
     steps:
       # Cancel any previous run of the test job
@@ -65,11 +65,7 @@ jobs:
         uses: conda-incubator/setup-miniconda@v2
         with:
           python-version: ${{ env.PYTHON }}
-          miniforge-variant: Mambaforge
-          use-mamba: true
           channels: conda-forge,defaults
-          # Needed for caching
-          use-only-tar-bz2: true
 
       - name: Collect requirements
         run: |
@@ -89,17 +85,11 @@ jobs:
           echo "Collected dependencies:"
           cat requirements-full.txt
 
-      - name: Setup caching for conda packages
-        uses: actions/cache@v3
-        with:
-          path: ~/conda_pkgs_dir
-          key: conda-${{ runner.os }}-${{ env.PYTHON }}-${{ hashFiles('requirements-full.txt') }}
-
       - name: Install requirements
-        run: mamba install --quiet --file requirements-full.txt python==$PYTHON
+        run: conda install --quiet --file requirements-full.txt python==$PYTHON
 
       - name: List installed packages
-        run: mamba list
+        run: conda list
 
       - name: Build source and wheel distributions
         run: |