Revert back of 'ONOS-7963 workflow invocation trigger on ONOS event'.

'ONOS-7963 workflow invocation trigger on ONOS event' needs to be
re-designed, and re-devloped.
So I revert back this.

Change-Id: I97f3cb38e466fb3c9e1a14a78ed69128977c2023
diff --git a/apps/workflow/api/src/main/java/org/onosproject/workflow/api/Workflow.java b/apps/workflow/api/src/main/java/org/onosproject/workflow/api/Workflow.java
index 01fb92d..3849afe 100644
--- a/apps/workflow/api/src/main/java/org/onosproject/workflow/api/Workflow.java
+++ b/apps/workflow/api/src/main/java/org/onosproject/workflow/api/Workflow.java
@@ -17,7 +17,6 @@
 
 import java.net.URI;
 import java.util.List;
-import java.util.Optional;
 import java.util.Set;
 
 /**
@@ -103,25 +102,10 @@
     List<ProgramCounter> getProgram();
 
     /**
-     * Returns worklet instance with given worklet Name.
-     * @param workletType worklet name
-     * @return Worklet
-     * @throws WorkflowException workflow exception
-     */
-
-    Worklet getTriggerWorkletInstance(String workletType) throws WorkflowException;
-
-    /**
      * Returns worklet description.
      * @param pc program counter
      * @return worklet description list
      */
     WorkletDescription getWorkletDesc(ProgramCounter pc);
 
-    /**
-     * Returns trigger worklet class name if any.
-     * @return trigger worklet class name
-     */
-    Optional<String> getTriggerWorkletClassName();
-
-    }
+}