[dbmanager] Fix error when opening SQL window

Author: m-kuhn

python/plugins/db_manager/dlg_sql_window.py

@@ -70,7 +70,6 @@ def __init__(self, iface, db, parent=None):
 
         self.editSql.setFocus()
         self.editSql.setVerticalScrollBarPolicy(Qt.ScrollBarAsNeeded)
-        self.editSql.setMarginVisible(True)
         self.initCompleter()
 
         # allow copying results