Fixing DRONE_TAG cleaner upper

.drone.yml

@@ -3,8 +3,9 @@ type: docker
 name: chessboard_builder
 
 trigger:
-  event:
-    - tag
+  ref:
+    include:
+      - refs/tags/builder-v*
 
 steps:
   - name: docker
@@ -14,15 +15,10 @@ steps:
       registry: git.pipsquire.com
       username:
         from_secret: docker_username
-      password:
         from_secret: docker_password
       tags:
         - latest
-        - ${DRONE_TAG//"builder-v"}
-    when:
-      ref:
-        include:
-          - refs/tags/builder-v*
+        - ${DRONE_TAG##builder-v}
 
 
 ---