Upgrade Kube client libraries 1.20.2→1.20.4

[LukeShu]

Description

This should make merging Douglas' Argo PR simpler. It seems that there
was actually no change in the client libraries between Kube 1.20.2 and
Kube 1.20.4, so that makes this whole thing a little silly, but it is what
it is; I do expect it to make the merge/rebase easier.

Related Issues

• [2.2] Support for receiving commands to manipulate Rollouts #4040

Testing

None.

Checklist

• I made sure to update CHANGELOG.md. - no applicable changes

  Remember, the CHANGELOG needs to mention:

  • Any new features
  • Any changes to our included version of Envoy
  • Any non-backward-compatible changes
  • Any deprecations

• This is unlikely to impact how Ambassador performs at scale. - turns out to be a no-op change

  Remember, things that might have an impact at scale include:

  • Any significant changes in memory use that might require adjusting the memory limits
  • Any significant changes in CPU use that might require adjusting the CPU limits
  • Anything that might change how many replicas users should use
  • Changes that impact data-plane latency/scalability

• My change is adequately tested. - turns out to be a no-op change

  Remember when considering testing:

  • Your change needs to be specifically covered by tests.
    • Tests need to cover all the states where your change is relevant: for example, if you add a behavior that can be enabled or disabled, you'll need tests that cover the enabled case and tests that cover the disabled case. It's not sufficient just to test with the behavior enabled.
  • You also need to make sure that the entire area being changed has adequate test coverage.
    • If existing tests don't actually cover the entire area being changed, add tests.
    • This applies even for aspects of the area that you're not changing – check the test coverage, and improve it if needed!
  • We should lean on the bulk of code being covered by unit tests, but...
  • ... an end-to-end test should cover the integration points

• I updated DEVELOPING.md with any any special dev tricks I had to use to work on this code efficiently. - no tricks

[kflynn]

Wow. That's... a lotta lines changed. 🙂 Hit it!!