Use homebrewed image for CI too

.drone.yml

@@ -8,16 +8,14 @@ steps:
       - shellcheck abra
 
   - name: run unit tests
-    image: docker:dind
+    image: decentral1se/docker-dind-bats-kcov
     commands:
-      - apk add bats git bash
       - bats tests
 
   - name: collect code coverage
     failure: ignore # until we fix this
-    image: kcov/kcov:38
+    image: decentral1se/docker-dind-bats-kcov
     commands:
-      - apt update && apt install -y bats git bash
       - kcov . bats tests || true
 
   - name: send code coverage report to codecov