!6305 Change log level from ERROR to DEBUG for debugger

Merge pull request !6305 from lichen_101010/change_log_level

mindspore/ccsrc/debug/debugger/debugger.cc

@@ -397,7 +397,7 @@ void Debugger::CommandLoop() {
     // get type of the command in reply
     DebuggerCommand cmd = GetCommand(reply);
     if (cmd == DebuggerCommand::kUnknownCMD) {
-      MS_LOG(ERROR) << "Error: debugger recieved unknown command";
+      MS_LOG(DEBUG) << "Debug: debugger recieved unknown command";
       continue;
     }