[skip ci] Bring CHANGELOG up to date

[vsppedro]

Unreleased

Backward-incompatible changes

• Drop support for Rails 5.2 and 6.0 as well as Ruby 2.6 and 2.7 they've been end-of-lifed by @dougmrqs and @HeitorMC.
  The gem now supports Ruby 3.0+ and Rails 6.1+. (#1521, #1522, #1547, #1548)

Bug fixes

• Fix validate_uniqueness_of matcher not supporting column of the type timestampz by @callahat. (#1544)
• Ensure that validation specs work for ActiveModel without ActiveRecord by @stonefield. (#1580)

Features

• Add normalize matcher by @stephannv. (#1558)
• Add support for Ruby 3.2 by @petergoldstein. (#1536)
• Add support for Ruby 3.3.0-rc1 by @mtasaka and @vsppedro. (#1579, #1588)
• Add support for Rails 7.1 by @matsales28. (#1573)
• Add support for array attributes on validate_length_of matcher by @jarenas9539. #1560
• Allow length validation on associations by @matsales28. (#1569)
• Improve have_db_index to better handle columns with multiple indexes by @abrom. (#1542)
• Implement of_sql_type qualifier on have_db_column matcher by @matsales28. (#1555)

Improvements

• When an unrelated error is seen with negated allow_value, give a hint by @matsales28. (#1570)

[matsales28]

LGTM! We're missing this new feature on the changelog.
#1560 Add support for array attributes on validate_length_of matcher.

Otherwise, it looks great! Thanks for working on this.

[vsppedro]

Nice catch! Thank you!