ES-9508 Realm prefix deprecation

Author: lukewhiting

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecks.java

@@ -280,7 +280,7 @@ static DeprecationIssue checkReservedPrefixedRealmNames(
             return new DeprecationIssue(
                 DeprecationIssue.Level.CRITICAL,
                 "Realm that start with [" + RESERVED_REALM_AND_DOMAIN_NAME_PREFIX + "] will not be permitted in a future major release.",
-                "https://www.elastic.co/guide/en/elasticsearch/reference/7.14/deprecated-7.14.html#reserved-prefixed-realm-names",
+                "https://ela.st/es-deprecation-7-realm-prefix",
                 String.format(
                     Locale.ROOT,
                     "Found realm "

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecksTests.java

@@ -220,7 +220,7 @@ public void testCheckReservedPrefixedRealmNames() {
         final DeprecationIssue deprecationIssue = deprecationIssues.get(0);
         assertEquals("Realm that start with [_] will not be permitted in a future major release.", deprecationIssue.getMessage());
         assertEquals(
-            "https://www.elastic.co/guide/en/elasticsearch/reference" + "/7.14/deprecated-7.14.html#reserved-prefixed-realm-names",
+            "https://ela.st/es-deprecation-7-realm-prefix",
             deprecationIssue.getUrl()
         );
         assertEquals(