flash_FP3_factory.sh: do NOT wipe userdata without asking (CLEAN_FLASH)

UPDATE 2025-05-13: Regression, see comment below.

The flash_FP3_factory.sh in the installation images from dev and stable should NOT wipe the userdata without explicitly asking!
Else the risk is just too high, that users might undesirably get their data erased.

Currently there's just a controlling variable CLEAN_FLASH inside the script. But that variable is always set to true, unless the user edits the script, recognized the variable and changes it.

I suggest to set CLEAN_FLASH to false by default and to include a little "enter WIPE to wipe" question into that script which sets CLEAN_FLASH to true.

 

''By the way: Where's the Git repo where that script is being developed?''