(CONT-874) Update changelog

Prior to this commit, it was brought to light an error in PR naming for
Puppet 8 support related PRs, where they failed to mention the potential
drop in Puppet 6 support. This commit aims to fix the changelog so that
it reflects better the changes made in this major update.

Author: LukasAud

CHANGELOG.md

@@ -8,7 +8,7 @@ All notable changes to this project will be documented in this file. The format
 
 ### Changed
 
-- \(CONT-850\) Puppet 8 compatibility [\#441](https://github.com/puppetlabs/puppetlabs-accounts/pull/441) ([LukasAud](https://github.com/LukasAud))
+- \(CONT-850\) Puppet 8 support / Drop Puppet 6 [\#441](https://github.com/puppetlabs/puppetlabs-accounts/pull/441) ([LukasAud](https://github.com/LukasAud))
 
 ## [v7.3.1](https://github.com/puppetlabs/puppetlabs-accounts/tree/v7.3.1) (2023-01-27)