Update New-AzOperationalInsightsStorageInsight.md

[thomast1906]

Please review my changes, current .Key1 does not return a value. As per my update I have included how to retrieve both Keys of storage account.

Description

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate change log has been updated
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • the changes have gone through a cmdlet design review (Microsoft internal partners only)
  • the cmdlet markdown files were generated using the platyPS module

[cormacpayne]

/azp run

[azure-pipelines]

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