Use `FutureWarning` instead of `DeprecationWarning` for deprecation warning

@puhuk is already working on this.

Since Jan 18, 2022.

*basically a copy of https://github.com/PyTorchLightning/metrics/issues/744 which was addressed in https://github.com/PyTorchLightning/metrics/pull/749*

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## 🚀 Feature

see suggestion in https://github.com/PyTorchLightning/metrics/pull/740#discussion_r782088021

### Motivation

most of the deprecations in TM are meant to users not developers

### Pitch
Replace `DeprecationWarning` with `FutureWarning` defined at:
https://github.com/PyTorchLightning/pytorch-lightning/blob/033dba1494a177954e8ca59bc74b1635e83b9efa/pytorch_lightning/utilities/warnings.py#L44
and remove:
https://github.com/PyTorchLightning/pytorch-lightning/blob/033dba1494a177954e8ca59bc74b1635e83b9efa/pytorch_lightning/utilities/warnings.py#L48-L49

### Alternatives
Keep using `DeprecationWarning`.

### Additional context

- **exception `DeprecationWarning`** Base class for warnings about deprecated features when those warnings are **intended for other Python developers**. _Ignored by the default warning filters_, except in the `__main__` module (PEP 565). Enabling the Python Development Mode shows this warning.

- **exception `FutureWarning`** Base class for warnings about deprecated features when those warnings are **intended for end users of applications** that are written in Python.

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