Treat IDREF mismatches as warnings in non-English translations

[jordikroon]

For non-English translations, IDREF mismatches should be treated as warnings instead of errors.
Outdated translations may reference IDs that have yet to be translated from doc-en, thus results in a CI failure.

[alfsb]

You can probably only count the lines that preg_match the message considered a warning. If the matched line count equals the output line count, then all lines are warned instead of errors, on translations.

    if ( ! is_array( $out ) )
        $out = [];
       
    $warnCount = 0;
    foreach ( $out as $line )
        if ( preg_match( $regex , $line ) )
            $warnCount++;
               
    $fatal = ( $isEnglish && count( $out ) > 0 ) || count( $out ) != $warnCount;

Let the errors be outputted as is. There is no point sileting warnings of real problems. There are other parts of configure.php that show warnings and do not abort the build as an error.