incorrect comment in bootstrap: stage 1 rustdoc *can* be used

[lolbinarycat]

The comment says that only stage 0 or stage 2 rustdoc is used, but the user can simply request stage 1 rustdoc.

rust/src/bootstrap/src/core/build_steps/tool.rs

Lines 667 to 672 in 8de4c72

	#[derive(Debug, Clone, Hash, PartialEq, Eq, Ord, PartialOrd)]
	pub struct Rustdoc {
	/// This should only ever be 0 or 2.
	/// We sometimes want to reference the "bootstrap" rustdoc, which is why this option is here.
	pub compiler: Compiler,
	}

tested by putting assert_ne!(self.compiler.stage, 1) in Rustdoc::run, then running ./x doc --stage 1 library/core, which causes the added assertion to fail.

[lolbinarycat]

Stage 1 rustdoc often makes sense to use in a lot of situations, such as when changing doc comments on rustc functions, and when also when modifying rustc functions that only exist for use by rustdoc and clippy, otherwise rustc will be rebuilt twice for each change you make

i believe stage0 rustdoc would work in the first situation, but not in the second.

i think the correct thing to do would just be to remove this comment, as stage1 rustdoc seems to work fine anyways.

[Kobzol]

This is fixed in #144303.