Remove randint, rand, rand_uniform and round_floats from utils.py

In https://gitlab.com/teklia/atr/dan/-/blob/main/dan/utils.py, multiple functions are defined using only the corresponding torch functions. We can remove these functions and directly call torch's:

• randint: https://gitlab.com/teklia/atr/dan/-/blob/14a54602f2ce89b8732da01a018765e459cec541/dan/utils.py#L19
• rand: https://gitlab.com/teklia/atr/dan/-/blob/14a54602f2ce89b8732da01a018765e459cec541/dan/utils.py#L26
• rand_uniform: https://gitlab.com/teklia/atr/dan/-/blob/14a54602f2ce89b8732da01a018765e459cec541/dan/utils.py#L33
• round_floats: https://gitlab.com/teklia/atr/dan/-/blob/14a54602f2ce89b8732da01a018765e459cec541/dan/utils.py#L152