azurerm_monitor_alert_prometheus_rule_group - rule block documentation fix

[crunchboy]

Community Note

• Please vote on this PR by adding a 👍 reaction to the original PR to help the community and maintainers prioritize for review
• Please do not leave comments along the lines of "+1", "me too" or "any updates", they generate extra noise for PR followers and do not help prioritize for review

Description

updated azurerm_monitor_alert_prometheus_rule_group documentation to reflect you can have multiple rule blocks

PR Checklist

• I have followed the guidelines in our Contributing Documentation.
• I have checked to ensure there aren't other open Pull Requests for the same update/change.
• I have checked if my changes close any open issues. If so please include appropriate closing keywords below.
• I have updated/added Documentation as required written in a helpful and kind way to assist users that may be unfamiliar with the resource / data source.
• I have used a meaningful PR title to help maintainers and other users understand this change and help prevent duplicate work.
  For example: “resource_name_here - description of change e.g. adding property new_property_name_here”

[stephybun]

Thanks @crunchboy LGTM 👍

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.