updated keras (#1445)

Signed-off-by: yes <[email protected]>

Author: tanwarsh

openfl-workspace/keras/torch/mnist/requirements.txt

@@ -1,4 +1,4 @@
-keras==3.8.0
+keras==3.9.0
 torch==2.6.0
 torch-xla==2.6.0
 torchvision==0.21.0