Update gateway listener compatibility doc

[pleshakov]

Proposed changes

(1)
Problem:
Documentation for certificateRefs of Gateway listener was out of date

Solution:
Update the documentation

Note:

• Namespace limitations was addressed in e6e149d
• Secret rotation was addressed in 890fddb

(2)
Problem:

• The api compatibility includes long lines that makes it difficult
  to edit and review
• Inconsistent indentation

Solution:

• Reformat the doc

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[kate-osborn]

@pleshakov how did you reformat? If I format the code in my Goland IDE I get a different output. Should we agree on a particular format so we don't just oscillate between different formats?

[pleshakov]

@pleshakov how did you reformat? If I format the code in my Goland IDE I get a different output. Should we agree on a particular format so we don't just oscillate between different formats?

@kate-osborn yep, Goland IDE. what are you rules?

This should be the ultimate agreement -- #555

[kate-osborn]

This should be the ultimate agreement -- #555

Perfect. Maybe we should prioritize this before we add more documentation.

I think the difference between my format rules and yours is tabs. The old spaces vs tabs debate.

[kate-osborn]

Approving. We can save the discussion about formatting for the markdown formatting issue.