[Sync EN] Clarify that PCRE delimiters must be ASCII characters (#4817) (#5223)

[github-actions]

Commit: https://github.com/php/doc-en/commit/61d512bfd7098a177b6490e0b478c72ed6fb90d6
PR: https://github.com/php/doc-en/pull/5223

Archivos ES a actualizar

• reference/pcre/pattern.syntax.xml