add PipelineStatus.CANCELING (#1248)

Author: jschneider

gitlab4j-models/src/main/java/org/gitlab4j/api/models/PipelineStatus.java

@@ -18,6 +18,7 @@ public enum PipelineStatus {
     SUCCESS,
     FAILED,
     CANCELED,
+    CANCELING,
     SKIPPED,
     MANUAL,
     SCHEDULED;