Deprecation removals for v0.3.0

[rg936672]

PR Type

• Removals
• Documentation content changes

Description

• Remove items slated for deprecation in v0.3.0 (closes Tracking issue for v0.3.0 deprecations #578)
• Deprecations now state what version they have been deprecated since
• Features deprecated in v0.3.0 (coreax.kernel, coreax.util.median_heuristic) are slated for removal in v0.4.0, not v0.3.0

How Has This Been Tested?

N/A

Does this PR introduce a breaking change?

No

(Write your answer here.)

Checklist before requesting a review

• I have made sure that my PR is not a duplicate.
• My code follows the style guidelines of this project.
• I have commented my code, particularly in hard-to-understand areas.
• I have performed a self-review of my code.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.

[github-actions]

Performance review

Commit 4b7bd80 - Merge 09aca34 into 8e097bf

No significant changes to performance.