No longer require master node to install Watcher templates (#85287) (#85294)

The master node was required to install Watcher index templates 
in earlier versions of 7.x to ensure that the master node was aware of
composable index templates. 

When upgrading to 8.x this is no longer an issue since all upgrade paths
require elder version of Elasticsearch to be on a version that is aware of 
composable index templates. 

This should fix #85043 by 
ensuring that the watcher history index template is always in place prior
to it's intended usage irregardless of the order of which nodes are upgraded.

Author: jakelandis

docs/changelog/85287.yaml

@@ -0,0 +1,6 @@
+pr: 85287
+summary: No longer require master node to install Watcher templates
+area: Watcher
+type: bug
+issues:
+ - 85043

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/WatcherIndexTemplateRegistry.java

@@ -94,12 +94,4 @@ public static boolean validate(ClusterState state) {
             .map(s -> Integer.valueOf(s.substring(s.lastIndexOf('-') + 1)))
             .anyMatch(version -> version >= 12);
     }
-
-    @Override
-    protected boolean requiresMasterNode() {
-        // These installs a composable index template which is only supported in early versions of 7.x
-        // In mixed cluster without this set to true can result in errors in the logs during rolling upgrades.
-        // If these template(s) are only installed via elected master node then composable templates are available.
-        return true;
-    }
 }