BUG#54832 - Comment for MyISAM says it is a default engine

Fixed MyISAM storage engine comment, so it doesn't anymore
state that MyISAM is default storage engine.

storage/myisam/ha_myisam.cc

@@ -2069,7 +2069,7 @@ mysql_declare_plugin(myisam)
   &myisam_storage_engine,
   "MyISAM",
   "MySQL AB",
-  "Default engine as of MySQL 3.23 with great performance",
+  "MyISAM storage engine",
   PLUGIN_LICENSE_GPL,
   myisam_init, /* Plugin Init */
   NULL, /* Plugin Deinit */