[tutorials] Added flash attention credits in tutorial

python/tutorials/06-fused-attention.py

@@ -1,6 +1,7 @@
 """
 Fused Attention
 ===============
+This is a Triton implementation of the Flash Attention algorithm (Dao et al., https://arxiv.org/pdf/2205.14135v2.pdf)
 """
 
 import pytest