Remove BWC in UpdateWatcherSettingsAction (#116686)

This removes code which was providing transport compatibility with
pre-8.15 nodes, which is not needed for 9.0.

At this point, the `readFrom` method is a one-liner, so it is inlined,
making the constructor public (which is more conventional).

Author: PeteGillinElastic

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/transport/actions/put/UpdateWatcherSettingsAction.java

@@ -7,7 +7,6 @@
 
 package org.elasticsearch.xpack.core.watcher.transport.actions.put;
 
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ActionType;
 import org.elasticsearch.action.ValidateActions;
@@ -17,7 +16,6 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.core.TimeValue;
-import org.elasticsearch.core.UpdateForV9;
 
 import java.io.IOException;
 import java.util.Map;
@@ -56,30 +54,14 @@ public Request(TimeValue masterNodeTimeout, TimeValue ackTimeout, Map<String, Ob
             this.settings = settings;
         }
 
-        public static Request readFrom(StreamInput in) throws IOException {
-            if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_15_0)) {
-                return new Request(in);
-            } else {
-                return new Request(TimeValue.THIRTY_SECONDS, TimeValue.THIRTY_SECONDS, in);
-            }
-        }
-
-        private Request(StreamInput in) throws IOException {
+        public Request(StreamInput in) throws IOException {
             super(in);
             this.settings = in.readGenericMap();
         }
 
-        @UpdateForV9(owner = UpdateForV9.Owner.DATA_MANAGEMENT) // bwc no longer required
-        private Request(TimeValue masterNodeTimeout, TimeValue ackTimeout, StreamInput in) throws IOException {
-            super(masterNodeTimeout, ackTimeout);
-            this.settings = in.readGenericMap();
-        }
-
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_15_0)) {
-                super.writeTo(out);
-            }
+            super.writeTo(out);
             out.writeGenericMap(this.settings);
         }
 

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/transport/actions/TransportUpdateWatcherSettingsAction.java

@@ -68,7 +68,7 @@ public TransportUpdateWatcherSettingsAction(
             clusterService,
             threadPool,
             actionFilters,
-            UpdateWatcherSettingsAction.Request::readFrom,
+            UpdateWatcherSettingsAction.Request::new,
             indexNameExpressionResolver,
             AcknowledgedResponse::readFrom,
             EsExecutors.DIRECT_EXECUTOR_SERVICE