[FIX] core.Popup: always use touch mode in mobile safari
[FIX] core.Popup: always use touch mode in mobile safari

- with the desktop mode in iPadOS 13, the touch mode was turned off in
  popup because the device is detected as touch enabled Macintosh and
  not iPad which is correct from the meaning of the new mode. However,
  since mobile safari never allows the focus to stay at a clicked button
  or link, the touch mode is always needed in mobile safari to make the
  "autoclose" feature work correctly.

BCP: 2070009967
Change-Id: I14cf60a0094df044f05026cb2691be473b007568

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5