branch-2.1: [fix](system) fix alter system modify hostname with valid ip exception #49551 (#49561)

cherry pick from #49551

fe/fe-core/src/main/java/org/apache/doris/analysis/ModifyNodeHostNameClause.java

@@ -64,8 +64,6 @@ public class ModifyNodeHostNameClause extends AlterClause {
                 // if no IP address for the host could be found, 'getByName'
                 // will throw UnknownHostException
                 InetAddress.getByName(newHost);
-            } else {
-                throw new AnalysisException("Invalid hostname: " + newHost);
             }
         } catch (UnknownHostException e) {
             throw new AnalysisException("Unknown hostname:  " + e.getMessage());