fix(import): collapse split clap imports in usage_md

perfectionist 34be521 (PR 173) fixes import_granularity so it now
detects multiple `use clap::...` statements that should be merged under
the `crate` style. Combine the two clap imports in src/usage_md.rs into
a single statement.

https://claude.ai/code/session_015ZyokLaZvcy5Yt8KpPxV3F

Author: claude

src/usage_md.rs

@@ -1,6 +1,5 @@
 use crate::args::Args;
-use clap::builder::PossibleValue;
-use clap::{Arg, ArgAction, Command, CommandFactory};
+use clap::{Arg, ArgAction, Command, CommandFactory, builder::PossibleValue};
 use derive_more::{Display, Error};
 use itertools::Itertools;
 use pipe_trait::Pipe;