docs: Update JAX backend array_type to jaxlib.xla_extension.ArrayImpl

[matthewfeickert]

Description

Update JAX backend array_type to jaxlib.xla_extension.ArrayImpl, which is a unified array type introduced in jaxlib v0.4.6.

• c.f. https://github.com/google/jax/releases/tag/jaxlib-v0.4.6
• c.f. Interacting with new jax array type jax-ml/jax#14768

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Update JAX backend array_type to jaxlib.xla_extension.ArrayImpl, which is a unified
  array type introduced in jaxlib v0.4.6.
   - c.f. https://github.com/google/jax/releases/tag/jaxlib-v0.4.6
   - c.f. https://github.com/google/jax/issues/14768

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (a4ec176) 98.30% compared to head (18b4a01) 98.30%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2134   +/-   ##
=======================================
  Coverage   98.30%   98.30%           
=======================================
  Files          69       69           
  Lines        4531     4531           
  Branches      645      645           
=======================================
  Hits         4454     4454           
  Misses         45       45           
  Partials       32       32           

Flag	Coverage Δ
contrib	97.88% <ø> (ø)
doctest	61.15% <ø> (ø)
unittests-3.10	96.31% <ø> (ø)
unittests-3.8	96.33% <ø> (ø)
unittests-3.9	96.35% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pyhf/tensor/jax_backend.py	98.61% <ø> (ø)

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[matthewfeickert]

I'm going to approve and merge this myself. As always, PRs approved by a single core dev can be reverted as needed by the rest of the dev team.