Fix: renameColumn syntax for daemonSecret

[keksgauner]

This fix the Unknown column error on migration.

After I changed from mysql to mariadb the latest version.
I got the error:

  2020_04_04_131016_add_table_server_transfers ........................................................................................ 71.15ms DONE
  2020_04_10_141024_store_node_tokens_as_encrypted_value .............................................................................. 72.99ms FAIL

In Connection.php line 825:
                                                                                                                                                                                         
  SQLSTATE[42S22]: Column not found: 1054 Unknown column '`daemonSecret`' in 'nodes' (Connection: mariadb, SQL: alter table `nodes` rename column ```daemonSecret``` to `daemon_token`)  
                                                                                                                                                                                         

In Connection.php line 571:
                                                                                      
  SQLSTATE[42S22]: Column not found: 1054 Unknown column '`daemonSecret`' in 'nodes'  

To Remove the ` fixed this.