Mark a doc comment block as text instead of ignore

[andiflabs]

Summary

A text block has been incorrectly marked with ignore. This means that cargo test considers the block as a doc test that shouldn't be compiled/run and is reported in its output.

Testing Plan

Run cargo test -p ironfish and verify that this line is gone:

test ironfish-rust/src/frost_utils/account_keys.rs - frost_utils::account_keys::derive_account_keys (line 29) ... ignored

Documentation

N/A

Breaking Change

N/A