chore(CHANGELOG): address review comments

this commit addresses some chores related to the package manifest, and
the changelog, noticed in review.

see:

- <prometheus#243 (comment)>
- <prometheus#243 (comment)>

Author: cratelyn

CHANGELOG.md

@@ -4,7 +4,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [0.24.0] - unreleased
+## [0.23.1] - unreleased
+
+### Changed
 
 - `Histogram::new` now accepts an `IntoIterator` argument, rather than an `Iterator`.
   See [PR 243].

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "prometheus-client"
-version = "0.23.0"
+version = "0.23.1"
 authors = ["Max Inden <[email protected]>"]
 edition = "2021"
 description = "Open Metrics client library allowing users to natively instrument applications."