Stop passing None to compile() in TF examples (#29597)

* Fix examples to stop passing None to compile(), rework example invocation for run_text_classification.py

* Add Amy's fix

examples/tensorflow/translation/run_translation.py

@@ -584,7 +584,7 @@ def main():
                 adam_global_clipnorm=training_args.max_grad_norm,
             )
         else:
-            optimizer = None
+            optimizer = "sgd"  # Just write anything because we won't be using it
         # endregion
 
         # region Metric and postprocessing