Fix invalid regex pattern.
Fix invalid regex pattern.

This was introduced as part of revision b8199ad1c4 ("Fixed handling of
multi-byte characters in both HttpServer and Duplicati") to resolve
issues #1063 and #1085.  However, the regex pattern was invalid.  This
reverts the pattern to the previous value, which seems more appropriate
since most non-standard encodings are of the form %uxxxx where xxxx is a
4 byte hex string representing a UTF-16 code.

This fixes issue #3737.

duplicati/duplicati,duplicati/duplicati,mnaiman/duplicati,mnaiman/duplicati,duplicati/duplicati,duplicati/duplicati,mnaiman/duplicati,duplicati/duplicati,mnaiman/duplicati,mnaiman/duplicati