Add rate limit units and error status

[hobti01]

Clarified the language in the rate limiting section to indicate units of measure, error codes, and the source of the client IP address.

What this PR does / why we need it: Documentation required some clarity in the rate limits section.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #3393

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[hobti01]

HI @aledbf , would you have a few moments for a documentation review?

[aledbf]

/ok-to-test

[aledbf]

@hobti01 please squash the commits, then this is ready to be merged

[codecov-io]

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@@            Coverage Diff            @@
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  Lines             ?     6749           
  Branches          ?        0           
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  Hits              ?     3985           
  Misses            ?     2335           
  Partials          ?      429

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[aledbf]

/lgtm

[aledbf]

@hobti01 thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, hobti01

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