Fix PyTorch version conflict in requirements.transformers.txt

Updated requirements.transformers.txt to match requirements.sam.txt:
- torch: >=2.0.1,<2.7.0 → >=2.8.0
- torchvision: >=0.15.0 → >=0.23.0
- Added: flash-attn>=2.8.2

This resolves the dependency conflict that was causing builds to fail.

Author: alexnorell

requirements/requirements.transformers.txt

@@ -1,6 +1,6 @@
-# TODO: update to 2.8.0 once pre-built flashattn is available
-torch>=2.0.1,<2.7.0
-torchvision>=0.15.0
+torch>=2.8.0
+torchvision>=0.23.0
+flash-attn>=2.8.2
 transformers>=4.53.3,<4.57.0
 timm~=1.0.0
 #accelerate>=0.32,<1.0.0