CSS-Automation: PS 7.4 only available in runtime environment

[MSNina123456]

clarify that PS 7.4 is only available in runtime environment experience.

[prmerger-automator[bot]]

@MSNina123456 : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod[bot]]

Learn Build status updates of commit 362e27c:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
articles/automation/automation-runbook-types.md	:white_check_mark:Succeeded

For more details, please refer to the build report.

[v-dirichards]

@jasminemehndir

Can you review the proposed changes?

Important: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged" @MicrosoftDocs/public-repo-pr-review-team

[jasminemehndir]

#sign-off