Update Android supported versions policy docs about LTS backward support

We decided to be supporting Android versions to already released LTS versions during their lifetime. So, for example Qt 6.5 initially supported Android 13, and now Android 14 (and soon 15) are released during its lifetime where now Qt LTS 6.5 would add support whenever they're released. This is to ensure, said Qt LTS release can still be used to publish to Play Store according to the changing Google Play Store target API version policy.