Bump squizlabs/php_codesniffer from 2.7.0 to 2.8.1

Bumps [squizlabs/php_codesniffer](https://github.com/squizlabs/PHP_CodeSniffer) from 2.7.0 to 2.8.1.
- [Release notes](https://github.com/squizlabs/PHP_CodeSniffer/releases)
- [Commits](squizlabs/PHP_CodeSniffer@2.7.0...2.8.1)

---
updated-dependencies:
- dependency-name: squizlabs/php_codesniffer
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>