add doc notes for database_roles

[schen59]

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

sql: add doc notes for database_roles

[github-actions]

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 1 file changed, 1 insertion(+))
google-beta provider: Diff ( 1 file changed, 1 insertion(+))

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 1 file changed, 1 insertion(+))
google-beta provider: Diff ( 1 file changed, 1 insertion(+))

[github-actions]

@BBBmau This PR has been waiting for review for 3 weekdays. Please take a look! Use the label disable-review-reminders to disable these notifications.