There is no functionality to just drop a quest, sorry.
(Every quest can have arbitrary requirements to start and to finish (succeed/fail). Which means there cannot really be a "drop/reacquire" quest option.)
If you are positive you won't be looking for a solution any more and *really* want to get rid of that quest, send us your save file and I'll fail the quest for you. (Here are the save file locations:
viewtopic.php?f=3&t=4624) Just this once!
![Wink ;)](./images/smilies/icon_e_wink.gif)