Auto merge of #4331 - joshtriplett:fix-notices, r=matklad

Auto merge of #4331 - joshtriplett:fix-notices, r=matklad

Remove inaccurate (misattributed) copyright notices

As discussed with @aturon, who took it to @rust-lang/core.

LICENSE-MIT and one source file contain inaccurate copyright notices of
the form "Copyright (c) (years) The Rust Project Developers", which
implies that an entity called "The Rust Project Developers" holds
copyrights in Rust. Rust contributors retain their copyrights, and do
not assign them to anyone by contributing.  Remove the inaccurate
notices.