remove redundant output when interrupting apply

The backend apply operation doesn't need to output the same text as the
cli itself. Instead notify the user that we are in the process of
stopping the operation.

backend/local/backend_apply.go

@@ -121,7 +121,7 @@ func (b *Local) opApply(
 	select {
 	case <-ctx.Done():
 		if b.CLI != nil {
-			b.CLI.Output("Interrupt received. Gracefully shutting down...")
+			b.CLI.Output("stopping apply operation...")
 		}
 
 		// Stop execution