Related for Rosh Hashanah 38:1

וחכמים מטהרין

whereas the Sages declare it clean'! - There is a difference of opinion between Tannaim [as to whether the Megillath Ta'anith, has been annulled], as it has been taught: 'These days which are mentioned in the Megillath Ta'anith are prohibited [to be kept as fast days] whether in the period when the Temple is standing or in the period when the Temple is not standing. So R'Meir.

Tosefta Rosh Hashanah (Lieberman)