[Sync EN] ext/mbstring: mb_*code_numericentity Clarify the ValueError conditions (#4852)

[github-actions]

Commit: https://github.com/php/doc-en/commit/3505aae96c190f3970e15bf3b7a12ead73b95662
PR: https://github.com/php/doc-en/pull/4852

Archivos ES a actualizar

• reference/mbstring/functions/mb-decode-numericentity.xml
• reference/mbstring/functions/mb-encode-numericentity.xml