chore: remove deprecated plugin wrapper (#53)

### What this PR does?
移除对已过时的 PluginWrapper 的引用

see also halo-dev/halo#6243 for more details

```release-note
None
```

src/main/java/run/halo/migrate/MigratePlugin.java

@@ -1,24 +1,24 @@
 package run.halo.migrate;
 
-import org.pf4j.PluginWrapper;
 import org.springframework.stereotype.Component;
 import run.halo.app.plugin.BasePlugin;
+import run.halo.app.plugin.PluginContext;
 
 /**
  * @author guqing
  * @since 2.0.0
  */
 @Component
 public class MigratePlugin extends BasePlugin {
-    
-    public MigratePlugin(PluginWrapper wrapper) {
-        super(wrapper);
+
+    public MigratePlugin(PluginContext pluginContext) {
+        super(pluginContext);
     }
-    
+
     @Override
     public void start() {
     }
-    
+
     @Override
     public void stop() {
     }