chore(drone): always pull image

Author: duanhongyi

.drone/drone.yml

@@ -9,7 +9,7 @@ platform:
 steps:
 - name: test
   image: docker.io/drycc/go-dev
-  pull: if-not-exists
+  pull: always
   privileged: true
   commands:
   - make bootstrap test
@@ -28,7 +28,7 @@ steps:
 
 - name: codecov
   image: docker.io/drycc/go-dev
-  pull: if-not-exists
+  pull: always
   commands:
   - curl -s https://codecov.io/bash | bash
   environment: