docs: highlights kubecost v2 breaking change

[cwyl02]

What problem does this PR solve?:
currently kubecost metadata overview doesn't include kubecost v2 breaking change

Which issue(s) does this PR fix?:

https://jira.nutanix.com/browse/NCN-105479

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Checklist

• If the PR adds a version bump, ensure there is no breaking change in Licensing model (or NA).
• If a chart is changed or app configuration is significantly changed, the chart version is correctly incremented (so that apps are not automatically upgraded from a previous version of DKP).

[github-actions]

✅ Created Kommander branch to test kommander-applications changes: https://github.com/mesosphere/kommander/tree/kapps/main/ychen/kubecostv2-doc-string

[msdolbey]

👍

[coveralls]

Pull Request Test Coverage Report for Build 13273837295

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 51.703%

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Totals
Change from base Build 13268164056:	0.0%
Covered Lines:	167
Relevant Lines:	323

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💛 - Coveralls