Fix workbooks deployment permissions documentation

[Copilot]

This PR updates the documentation related to the permissions required for deploying FinOps workbooks. The original documentation incorrectly stated that Reader access was sufficient to deploy workbooks, which is not true when using the ARM template deployment method.

Changes made:

• Updated the permission requirements across all workbooks documentation:

  • Clarified that Contributor role or a role with Microsoft.Resources/deployments/validate/action permission is required for ARM template deployments
  • Specified that Workbook Contributor role is for saving workbooks after deployment
  • Maintained that Reader role is for viewing workbook tabs

• Added alternative deployment instructions for users with only Reader access:

  • Added step-by-step instructions for downloading workbook files directly from GitHub
  • Added instructions for importing workbooks directly into Azure Monitor (which works with Reader access)
  • Included links to the correct repository locations for the workbook files

• Ensured consistency across all related documentation files:

  • docs-mslearn/toolkit/workbooks/finops-workbooks-overview.md
  • docs-mslearn/toolkit/workbooks/customize-workbooks.md
  • docs/workbooks.md
  • src/templates/finops-workbooks/README.md

These changes address the issue where users with only Reader access are unable to deploy workbooks using the ARM template method, and provide clear alternatives for those users.

Fixes #1612.

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[flanakin]

Suggested change

	To deploy FinOps workbooks using ARM templates, you need:
	- **Contributor** role or a role with `Microsoft.Resources/deployments/validate/action` permission
	- **Workbook Contributor** role to save workbooks after deployment
	- **Reader** role to view all workbook tabs
	> If you only have Reader access, you can download the workbook files from the [GitHub repository](https://github.com/microsoft/finops-toolkit/tree/main/src/workbooks) and import them directly into Azure Monitor Workbooks.
	FinOps workbooks require the <strong>Workbook Contributor</strong> role to deploy and <strong>Reader</strong> on all subscriptions you want to monitor.

[Copilot]

Simplified the permissions section with your suggested wording that's more concise and accurate. Commit de144d6

[flanakin]

Suggested change

	FinOps workbooks require the <strong>Contributor</strong> role or a role with both <strong>Microsoft.Resources/deployments/validate/action</strong> and <strong>Microsoft.Resources/deployments/write</strong> permissions for ARM template deployments, <strong>Workbook Contributor</strong> role to save changes, and <strong>Reader</strong> on all subscriptions you want to monitor.
	> If you only have Reader access, you can download the workbook files from the [GitHub repository](https://github.com/microsoft/finops-toolkit/tree/main/src/workbooks) and import them directly into Azure Monitor Workbooks.
	FinOps workbooks require the <strong>Workbook Contributor</strong> role to deploy and <strong>Reader</strong> on any subscriptions you want to monitor.