Unreasonable dependency on really old dm-control

Hi. See the error below:

`The conflict is caused by:
The user requested dm-control>=1.0.19
dm-acme[envs,jax,tf] 0.4.0 depends on dm-control==0.0.364896371`

You'll easily reproduce this with a two-line requirements.txt file.

I have to confess I'm pretty underwhelmed with the quality of the Python packaging of the libraries coming out of DeepMind. Writing all this software, open-sourcing it, to only make it impossible for consumers to integrate it is... illogical.