Last 3.x minor | Hard deprecate old-style setting of array properties

[jrfnl]

PHPCS 3.3.0 (June 2018) introduced a new XML format to pass custom array properties to sniffs.

Support for the old-style comma-separate string format for passing array values was deprecated in PHPCS 3.3.0 and support for the old format will be removed in PHPCS 4.0 as discussed in squizlabs/PHP_CodeSniffer#1665

I think it would be prudent to add a deprecation notice in one of the last 3.x minors to bring this to the attention of ruleset maintainers who haven't updated their ruleset yet.

Refs:

• https://github.com/PHPCSStandards/PHP_CodeSniffer/releases/tag/3.3.0
• Feature - define arrays in ruleset squizlabs/PHP_CodeSniffer#1665