Update CITATION.cff

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: LoserCheems

CITATION.cff

@@ -1,5 +1,5 @@
 cff-version: "1.2.0"
-date-released: 2025-6
+date-released: 2025-06
 message: "If you use this software, please cite it using these metadata."
 title: "Flash Dynamic Mask Attention: Trainable Dynamic Mask Sparse Attention"
 url: "https://github.com/SmallDoges/flash-dmattn"