This quest is a Repeatable quest.
Repeatable quests are quests that can be completed more than once. It's possible that any experience or reputation rewards are only rewarded the first time this quest is completed, but nevertheless, completing this quest will not make it appear as completed in the Wowhead quest tracker, and it can therefore be safely excluded if you're a completionist.
Examples of Repeatable quests:
- Buff quests.
Most common example. You collect certain items that can be gathered even after completing the associated buff quest once. Turning them in may grant a buff. These quests are repeatable so that you can refresh the buff anytime, by completing the quest again.
- Item quests.
Uncommon. Quests that reward you an item which, for example, is required in another quest. Sometimes these quests are repeatable so that you can get more of these items if necessary.