This is necessary to ensure we can correctly detect PJRT plugins via
entry_points without compatibility errors.
Prior to this change, there was conditional logic to handle if
importlib_metadata wasn't installed at all. However, it doesn't handle
the case where importlib_metadata is installed by not high enough
version to support Python 3.10 compat. This change gets rid of that
logic and just ensures the right version is installed.
All of this logic can be removed if/when jax requires Python version
>= 3.10
This also removes an unnecessary `requests` dep for the [tpu] install.