macOS a11y: collapse branches on identical condition

No need to test twice whether the row's columns array is initialized.

Pick-to: 6.8
Change-Id: Iead06f98ad421202bb4b71ae8efbd784ab3e87c1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit bd6e55c856e3c016048410f69919e443c71628bf)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/platforms/cocoa/qcocoaaccessibilityelement.mm

@@ -159,8 +159,6 @@ static void convertLineOffset(QAccessibleTextInterface *text, int *line, int *of
                                 qCWarning(lcAccessibilityTable)
                                         << "Table representation column count is out of sync:"
                                         << rowElement->columns.count << "!=" << tableInterface->columnCount();
-                            }
-                            if (rowElement->columns) {
                                 [rowElement->columns autorelease];
                                 rowElement->columns = nil;
                             }