Replacing kits does not replaces the Toolchain and board SDK paths

While changing the MCU SDK to the other/older version of QT for MCU, the toolchain path and board SDK paths were not replaced.

Steps to reproduce:

1. Open QTC from the latest Qt for MCU installation (e.g. I used 2.4.0 SDK)
2. Check if the kits were autogenerated for the selected MCU version
3. Now go to Edit -> Preferences -> Devices -> MCU
4. Change the MCU SDK path to the older Qt for MCU SDK (I changed to 2.3.1)
5. Click Apply and choose to Replace existing kits option from the popup window
6. Now go to Edit -> Preferences -> Kits
7. select any kit and check its CMake configurations
8. You can see the Board SDK directory path and the Toolchain paths were not replaced at all.