BOSTON — In recent weeks, as Golden State won seven games in a row by double-digit points, many have wondered whether it would face a significant threat. During their 92-88 win over the Warriors on Thursday night at TD Garden, the Celtics left little doubt: It could make things interesting come June. The Celtics held a Golden State team that opened the night averaging 119.6 points — 8.2 more than any other club — under 100 points for just the second time this season and to 40.2 percent shooting from the field (31.3 percent from three-point range). In his first game back from a thigh injury, Stephen Curry mustered only nine points on 3-for-14 shooting and finished with a plus-minus of minus-14.