Instructions on website for CLI usage are incorrect

All the examples on the website suggest doing
`keybase pgp encrypt maria -m 'this is a secret'`
but the current CLI version (0.8.23) doesn't support this and just uses
`keybase encrypt maria -m 'this is a secret'`

keybase: error: argument "subcommand_name": Invalid choice: pgp (choose from [btc, bitcoin, cert, dir, code-sign, config, decrypt, dec, encrypt, enc, help, id, identify, join, signup, keygen, gen, generate, list-signatures, list-sigs, list-tracking, login, logout, pull, push, prove, proof, reset, nuke, revoke, revoke-signatures, revoke-sig, search, sign, sig, status, switch, track, untrack, unverify, verify, version, vers])

Locate the website instructions containing the `keybase pgp encrypt` example and compare them with the listed current CLI commands. Update the affected examples to use the supported command form, then run the example to confirm it no longer reports `pgp` as an invalid subcommand.

Written by the indexing model from the issue text.