chore: add CHANGELOG entry for imports_granularity=Module changes

Author: ytmimi

CHANGELOG.md

@@ -33,6 +33,8 @@
 - Begin initial formatting for `use closures` and `use chains` (`#![feature(ergonomic_clones)]`). Previously, the closure and chain was left as the developer wrote it [#6532](https://github.com/rust-lang/rustfmt/pull/6532)
 - The unstable `required_version` configuration option now support semantic versioning [#6063](https://github.com/rust-lang/rustfmt/issues/6063)
 - Format `lazy_static::lazy_static!` like `lazy_static!` when setting `style_edition=2027` [#6287](https://github.com/rust-lang/rustfmt/issues/6287)
+- Top-level imports are no longer merged when setting `imports_granularity=Module`. Note that `imports_granularity=Module` is still an unstable configuration [#6191](https://github.com/rust-lang/rustfmt/issues/6191)
+
 
 ### Added
 - Add `style_edition=2027` to gate unstable formatting [#6324](https://github.com/rust-lang/rustfmt/pull/6324)