move strict provenance lints to new feature gate, remove old feature gates

Author: RalfJung

compiler/rustc_arena/src/lib.rs

@@ -23,7 +23,6 @@
 #![feature(maybe_uninit_slice)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
-#![feature(strict_provenance)]
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 

compiler/rustc_codegen_ssa/src/lib.rs

@@ -10,7 +10,6 @@
 #![feature(let_chains)]
 #![feature(negative_impls)]
 #![feature(rustdoc_internals)]
-#![feature(strict_provenance)]
 #![feature(try_blocks)]
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end