chore(dylint): drop unnecessary register_tool attributes from ai_instructions

The `feature(register_tool)` and `register_tool(perfectionist)` crate
attributes were only required to support the `perfectionist::lint_silence_reason`
suppression, which has since been removed. With no remaining
`perfectionist::` attributes in the file, these are dead and can go.

https://claude.ai/code/session_015ZyokLaZvcy5Yt8KpPxV3F

Author: claude

cli/ai_instructions.rs

@@ -1,6 +1,3 @@
-#![cfg_attr(dylint_lib = "perfectionist", feature(register_tool))]
-#![cfg_attr(dylint_lib = "perfectionist", register_tool(perfectionist))]
-
 use clap::Parser;
 use derive_more::Display;
 use pipe_trait::Pipe;