std::error::Error trait doc still talks about `cause()`

[Arnavion]

rust/src/libstd/error.rs

Lines 43 to 48 in a9ff135

	/// The [`cause`] method is generally used when errors cross "abstraction
	/// boundaries", i.e., when a one module must report an error that is "caused"
	/// by an error from a lower-level module. This setup makes it possible for the
	/// high-level module to provide its own errors that do not commit to any
	/// particular implementation, but also reveal some of its implementation for
	/// debugging via [`cause`] chains.

This should be updated to talk about source() instead.