Remove existing docker image before building in PR tests

Author: hdunham

.github/workflows/pull_request_tests.yml

@@ -26,6 +26,8 @@ jobs:
         env:
           NREL_DEV_API_KEY: ${{ secrets.NREL_DEV_API_KEY }}
         run: ./.github/scripts/make_keys.py.sh 
+      - name: Remove existing base-api-image
+        run: docker rmi docker.io/library/base-api-image:latest || true
       - name: Build containers
         run: docker compose up -d
       - name: Check running containers