useless_format lint gives a wrong example for "Good"

[ColinFinck]

The description of the useless_format lint gives the following "Bad" and "Good" examples:

rust-clippy/clippy_lints/src/format.rs

Lines 30 to 35 in d783e3d

	/// // Bad
	/// # let foo = "foo";
	/// format!("{}", foo);
	///
	/// // Good
	/// format!("foo");

However, the "Good" example is something that is also not accepted by the useless_format lint.

[mgacek8]

@rustbot claim