[browser] Correctly refresh postgres schemas when dropping tables

(cherry-picked from 5a41748)

src/providers/postgres/qgspostgresdataitems.cpp

@@ -691,9 +691,13 @@ bool QgsPGSchemaItem::handleDrop( const QMimeData * data, Qt::DropAction )
 {
   QgsPGConnectionItem *conn = qobject_cast<QgsPGConnectionItem *>( parent() );
   if ( !conn )
-    return 0;
+    return false;
+
+  bool result = conn->handleDrop( data, mName );
+  if ( result )
+    refresh();
 
-  return conn->handleDrop( data, mName );
+  return result;
 }
 
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