Remove erroneous comment.

nnethercote · nnethercote · commit 1aa48a002a83 · 2024-05-01T08:42:51.000+10:00
The comment was originally in `src/librustc_mir/lib.rs`, but now that
it's in `compiler/rustc_const_eval/src/lib.rs` it's no longer
appropriate.
diff --git a/compiler/rustc_const_eval/src/lib.rs b/compiler/rustc_const_eval/src/lib.rs
@@ -1,9 +1,3 @@
-/*!
-
-Rust MIR: a lowered representation of Rust.
-
-*/
-
 #![allow(internal_features)]
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![feature(rustdoc_internals)]
