Fix gradient accumulation in tf2

Author: Corey Adams

src/utils/tensorflow2/trainer.py

@@ -653,7 +653,7 @@ def train_step(self):
 
         # After the accumulation, weight the gradients as needed and apply them:
         if self.args.gradient_accumulation != 1:
-            gradients /= self.args.gradient_accumulation
+            gradients = [ g / self.args.gradient_accumulation for g in gradients ]
 
         self.apply_gradients(gradients)