fix failing examples

[Borda]

🐛 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...