fix failing examples
🐛 Bug
We have uncommented PL examples in #4551 but two of them turned to be failing and shall be fixed:
FAILED pl_examples/test_examples.py::test_examples_dp_image_classifier[\n--max_epochs 1 --batch_size 32 --limit_train_batches 2 --limit_val_batches 2 --gpus 2 --distributed_backend dp --precision 16 ]
FAILED pl_examples/test_examples.py::test_examples_dp_autoencoder[\n--max_epochs 1 --batch_size 32 --limit_train_batches 2 --limit_val_batches 2 --gpus 2 --distributed_backend dp --precision 16 ]

To Reproduce
uncomment two remaining examples with TODO comment
Environment
Drone Multi-GPU testing
Additional context
get back full example testing...