[DOC] Add back Rust 1.85.0 requirement to NEWS.md (ruby#15728)

* [DOC] Add back Rust 1.85.0 requirement to NEWS.md

Addresses k0kubun's review in ruby#15711 (comment)

NEWS.md serves both CRuby developers as well as end-users. As the
release date closes in, it probably gets seen by more users than
core developers (on the blog for example).

Most users probably don't build Ruby by hand, and instead that is
abstracted through tools like ruby-install or a package manager.
For some users these tools may install pre-built binaries where
they exist, in which case the Rust requirement doesn't apply. In
other instances, the tools merely automate the build, in which case
the correct rustc version is required to enable support.

It is also a little confusing to talk about "enabling support for
the JIT during the build" vs "enabling the JIT at runtime".

This copy attempts to balance all of the above and hopefully gets
the correct points across all intended audiences.

* Apply suggestion from k0kubun

Co-authored-by: Takashi Kokubun <[email protected]>

---------

Co-authored-by: Takashi Kokubun <[email protected]>

Author: chancancode

NEWS.md

@@ -570,7 +570,8 @@ A lot of work has gone into making Ractors more stable, performant, and usable.
 
 * ZJIT
     * Introduce an [experimental method-based JIT compiler](https://docs.ruby-lang.org/en/master/jit/zjit_md.html).
-      To enable ZJIT on supported platforms, supply the `--zjit` option or call `RubyVM::ZJIT.enable` at runtime.
+      Where available, ZJIT can be enabled at runtime with the `--zjit` option or by calling `RubyVM::ZJIT.enable`.
+      When building Ruby, Rust 1.85.0 or later is required to include ZJIT support.
     * As of Ruby 4.0.0, ZJIT is faster than the interpreter, but not yet as fast as YJIT.
       We encourage experimentation with ZJIT, but advise against deploying it in production for now.
     * Our goal is to make ZJIT faster than YJIT and production-ready in Ruby 4.1.