Composer.lock: update CS dependencies

[jrfnl]

Summary

This PR can be summarized in the following changelog entry:

• N/A

Relevant technical choices:

• PHPCS has released version 3.4.2.
• WPCS has released version 2.1.0.

Refs:

• https://github.com/squizlabs/PHP_CodeSniffer/releases/tag/3.4.1
• https://github.com/squizlabs/PHP_CodeSniffer/releases/tag/3.4.2
• https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/releases/tag/2.1.0

Test instructions

This PR can be tested by following these steps:

• N/A If the build passes, we're good.

[johannadevos]

CR 👍