Remove get_gpu_memory_map deprecated since v1.5

[akihironitta]

What does this PR do?

Part of #15618.
The API was deprecated in #9921.

Does your PR introduce any breaking changes? If yes, please list them.

Removes

pytorch_lightning.utilities.memory.get_gpu_memory_map

in favor of

pytorch_lightning.accelerators.cuda.get_nvidia_gpu_stats

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cc @Borda @justusschock @awaelchli @akihironitta

[akihironitta]

Not sure which milestone this change is part of, v1.8.x or v1.9.

[awaelchli]

Not sure which milestone this change is part of, v1.8.x or v1.9.

Removals of deprecated API always goes to milestone 1.X.0 :)

[Borda]

Not sure which milestone this change is part of, v1.8.x or v1.9.

Removals of deprecated API always goes to milestone 1.X.0 :)

On the other hand this is supposed to be removed already fro 1.7.0 😇