Fix Qt-RangeLoopDetach in qgeofiletilecacheosm.cpp

- use std::as_const() where possible, and introduce an intermediate
  local const variable where it is not.

Axivion-Id: qt_Add-ons_qtlocation_dev_linux:SV257
Axivion-Id: qt_Add-ons_qtlocation_dev_linux:SV258
Axivion-Id: qt_Add-ons_qtlocation_dev_linux:SV259
Axivion-Id: qt_Add-ons_qtlocation_dev_linux:SV260
Axivion-Id: qt_Add-ons_qtlocation_dev_linux:SV261
Axivion-Id: qt_Add-ons_qtlocation_dev_linux:SV262
Task-number: QTBUG-144760
Pick-to: 6.12 6.11 6.8
Change-Id: I6c9fbf45bce4ad64ef611f9eab2451db0cd6f831
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>