Move minimum requirements file... again (torchgeo#646)

Author: adamjstewart

.github/workflows/tests.yaml

@@ -85,7 +85,7 @@ jobs:
     - name: Install pip dependencies
       run: |
         pip install cython numpy==1.17.2  # needed by pycocotools
-        pip install -r .github/requirements-min.txt
+        pip install -r requirements/min
         pip list
     - name: Run pytest checks
       run: pytest --cov=torchgeo --cov-report=xml