Update TypeSpec API Specification for Microsoft.CodeTransparency

[praveenkuttappan]

This pull request includes changes to the TypeSpec API specification for the Microsoft.CodeTransparency service, including updates to the CreateEntryPending model and other related operations. It aims to enhance the API's compliance with the IETF SCITT draft.

[openapi-pipeline-app]

Next Steps to Merge

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• ❌ This PR targets either the main branch of the public specs repo or the RPSaaSMaster branch of the private specs repo. These branches are not intended for iterative development. Therefore, you must acknowledge you understand that after this PR is merged, the APIs are considered shipped to Azure customers. Any further attempts at in-place modifications to the APIs will be subject to Azure's versioning and breaking change policies. Additionally, for control plane APIs, you must acknowledge that you are following all the best practices documented by ARM at aka.ms/armapibestpractices. If you do intend to release the APIs to your customers by merging this PR, add the PublishToCustomers label to your PR in acknowledgement of the above. Otherwise, retarget this PR onto a feature branch, i.e. with prefix release- (see aka.ms/azsdk/api-versions#release--branches).
• ❌ Your PR requires an API stewardship board review as it introduces a new API version (label: new-api-version). Schedule the review by following aka.ms/azsdk/onboarding/restapischedule.
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[openapi-pipeline-app]

PR validation pipeline started successfully. If there is ApiView generated, it will be updated in this comment.

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

Language	API Review for Package
TypeSpec	Microsoft.CodeTransparency
Python	azure-codetransparency
Java	com.azure:azure-security-codetransparency
JavaScript	@azure-rest/codetransparency-rest

[weidongxu-microsoft]

I assume this file need to be reviewed by EngSys?

[weidongxu-microsoft]

Versioning by @added(Versions.v2025_05_31_preview)?

(you would need to use name-value in enum
https://typespec.io/docs/language-basics/enums/

[weidongxu-microsoft]

Unsure if you want an offline review (if the only change is add 1 property).