update ENTER_TRADE_IN_MODE permission description

ENTER_TRADE_IN_MODE is a permission that has been extended to cover
go/android-diagnostics-hal use cases for adb shell tradeinmode
getstatus. Updating the description here to explain the potential naming
confusion

Bug: 397154502
Flag: com.android.tradeinmode.flags.trade_in_mode_2025q4
Test: th
Change-Id: I6bc62fe2415161e54c007b0bba9ed32c87d397d7