release 3.3.1

Edit: on May 11, 2023 the Debian/Ubuntu packages were updated from 3.3.1-1 to 3.3.1-2 because of packaging bug OpenIDC/liboauth2#46

Bugfixes

• clean WWW-Authenticate header in main request as well if this is a subrequest; closes #42
  this avoids the WWW-Authenticate header to be sent in HTTP 200 responses; thanks @ErmakovDmitriy

Packaging

• depend on liboauth2 >= 1.4.5.3
• the liboauth2 dependencies can be found here: https://github.com/OpenIDC/liboauth2/releases.