chore: fix `codeigniter/coding-standard` version to `1.7.*`

[kenjis]

Description coding-standard 1.8.0 enables rules for PHP 8.1. So we cannot use it unless we drop PHP 7.4 support.

Checklist:

• [x] Securely signed commits
• [ ] Component(s) with PHPDoc blocks, only if necessary or adds value
• [ ] Unit testing, with >80% coverage
• [ ] User guide updated
• [x] Conforms to style guide