Pull newest Gitea dev image always (#581)

Reviewed-on: https://gitea.com/gitea/go-sdk/pulls/581
Reviewed-by: Gusted <williamzijl7@hotmail.com>
Reviewed-by: 6543 <6543@obermui.de>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-committed-by: John Olheiser <john.olheiser@gmail.com>

.drone.yml

@@ -13,6 +13,7 @@ workspace:
 steps:
 - name: gitea
   image: gitea/gitea:dev
+  pull: always
   detach: true
   commands:
   - mkdir -p /tmp/conf/