Broken link to anchor docs #222
Description
In the passage Anchor instruction data uses a unique [Anchor discriminator](https://book.anchor-lang.com/anchor_bts/discriminator.html) to determine which instruction is called. in https://docs.solanamobile.com/android-native/using-anchor-programs, there's a link to https://www.anchor-lang.com/anchor_bts/discriminator.html which no longer works.
Perhaps it should be replaced by https://www.anchor-lang.com/docs/basics/idl#discriminators?