Remove guava dependency (#1776)

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

hawkbit-rest/hawkbit-mgmt-api/src/main/java/org/eclipse/hawkbit/mgmt/json/model/MgmtPollStatus.java

@@ -18,8 +18,6 @@ import lombok.Data;
 import lombok.ToString;
 import lombok.experimental.Accessors;
 
-import static org.checkerframework.checker.units.qual.Prefix.exa;
-
 /**
  * A json annotated rest model for PollStatus to RESTful API representation.
  */