UI/Qt: Submit autocomplete selections directly

When Return is pressed while the autocomplete popup is visible, submit
the location edit directly instead of falling through to QLineEdit's
default key handling after closing the popup. This keeps the omnibox
responsive to Return after chrome layout changes rebuild nearby widgets.

UI/Qt/LocationEdit.cpp

@@ -487,6 +487,9 @@ void LocationEdit::keyPressEvent(QKeyEvent* event)
             m_is_applying_inline_autocomplete = false;
         }
         m_autocomplete->close();
+        emit returnPressed();
+        event->accept();
+        return;
     }
 
     if (should_suppress_inline_autocomplete_for_key(event))