follow-up plugins changes: fix qml gui

follow-up https://github.com/spesmilo/electrum/pull/8713

```
  1.35 | E | __main__ | daemon.run_gui errored
Traceback (most recent call last):
  File "/home/user/wspace/electrum/./run_electrum", line 458, in handle_cmd
    d.run_gui()
  File "/home/user/wspace/electrum/electrum/daemon.py", line 623, in run_gui
    self.gui_object = gui.ElectrumGui(config=self.config, daemon=self, plugins=self._plugins)
  File "/home/user/wspace/electrum/electrum/util.py", line 482, in do_profile
    o = func(*args, **kw_args)
  File "/home/user/wspace/electrum/electrum/gui/qml/__init__.py", line 82, in __init__
    self.app = ElectrumQmlApplication(sys.argv, config=config, daemon=daemon, plugins=plugins)
  File "/home/user/wspace/electrum/electrum/gui/qml/qeapp.py", line 428, in __init__
    self.plugins.load_plugin('trustedcoin')
  File "/home/user/wspace/electrum/electrum/plugin.py", line 269, in load_plugin
    raise Exception(f"could not find plugin {name!r}")
Exception: could not find plugin 'trustedcoin'
```

electrum/gui/qml/qeapp.py

@@ -425,7 +425,7 @@ class ElectrumQmlApplication(QGuiApplication):
             "MEMPOOL_MB":            electrum.util.UI_UNIT_NAME_MEMPOOL_MB,
         })
 
-        self.plugins.load_plugin('trustedcoin')
+        self.plugins.load_internal_plugin('trustedcoin')
 
         qInstallMessageHandler(self.message_handler)