[Sync EN] ext/pcre: document variable-length lookbehind and longer subpattern names (PHP 8.4) (#5739)

[github-actions]

Commit: https://github.com/php/doc-en/commit/c083c88c8e7ed7eb0d14662c0471693dcac42daf
PR: https://github.com/php/doc-en/pull/5739

Archivos ES a actualizar

• reference/pcre/pattern.syntax.xml