Why do you need to get rid of it? Just ignore it if you do not want to do those quests, it is just one journal entry, you are bound to get stuck with more than one journal entry if you have a long list to work your way through.
I agree with aussie, it's kind of a drag, but I don't know anyone who's not had quests stuck in their journal.
On the other hand, have you ever done the TG questline? It's actually more fun that I thought it would be, and they aren't the evil nasties I thought, not like the Brotherhood. I avoided it for ages, but finally did a character just for that and had a lot of fun with it.
You don't. Removing quests from the journal has never been a feature in Elder Scrolls games.
Best you can do is deactivate the quest and turn it off. As you get more, it will eventually drop to the bottom of the list.
You can't remove it or hide or anything like that, you just need to either
A. Finish it.
B. Ignore it.
Other than that you are SOL.