Improve setting deprecation message (#23156)

This change modifies the deprecation log message emitted when a setting
is found which is deprecated. The new message indicates docs for the
deprecated settings can be found in the breaking changes docs for the
next major version.

closes #22849

Author: rjernst

core/src/main/java/org/elasticsearch/common/settings/Setting.java

@@ -344,8 +344,8 @@ protected void checkDeprecation(Settings settings) {
         if (this.isDeprecated() && this.exists(settings)) {
             // It would be convenient to show its replacement key, but replacement is often not so simple
             final DeprecationLogger deprecationLogger = new DeprecationLogger(Loggers.getLogger(getClass()));
-            deprecationLogger.deprecated("[{}] setting was deprecated in Elasticsearch and it will be removed in a future release! " +
-                "See the breaking changes lists in the documentation for details", getKey());
+            deprecationLogger.deprecated("[{}] setting was deprecated in Elasticsearch and will be removed in a future release! " +
+                "See the breaking changes documentation for the next major version.", getKey());
         }
     }