[Sync EN] Update pattern.syntax.xml; meta-characters (#3057)

[github-actions]

Commit: https://github.com/php/doc-en/commit/c414a81646ee424d1814725f54ec86b9a8f6b434
PR: https://github.com/php/doc-en/pull/3057

Archivos ES a actualizar

• reference/pcre/pattern.syntax.xml