updates cloud security section of billing page

[benironside]

Resolves #5166. Updates the serverless billing page to reflect the changes to which cloud assets we will bill for, for customers using serverless.

Preview: Security billing dimensions

[github-actions]

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[mergify]

This pull request does not have a backport label. Could you fix it @benironside? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• v7.x is the label to automatically backport to the 7.x branch.
• v7./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[benironside]

run docs-build

[elasticdocs]

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[smriti0321]

@benironside Please review the additional ask in the comment- #5166 (comment) and help with latest information in document. Thank you!

[smriti0321]

Thanks @benironside, it looks good.

[nastasha-solomon]

Looks great! Left some suggestions for your consideration. : )

[nastasha-solomon]

Suggested change

	For <DocLink id="serverlessSecurityD4cOverview" text="D4C"/>, billing is per protected agent (per `agent.id`).
	For <DocLink id="serverlessSecurityD4cOverview" text="D4C"/>, billing is measured by each protected agent (per `agent.id`) that you use.