Update JSDoc for optional options

[angrycat9000]

Updates IonImageryProvider.fromAssetId and Cesium3DTileset.fromIonAssetId to have optional options. In both cases options arguments were not marked as optional in JSDoc causing them to be required in Typescript.

Fixes #11623 and fixes #11624

Test Plan

Run npm build-ts

Open the generated typescript definition file, and verify that both methods now include optinons?: instead of options: to mark them as optional

 static fromAssetId(assetId: number, options?: IonImageryProvider.ConstructorOptions): Promise<IonImageryProvider>;

 static fromIonAssetId(assetId: number, options?: Cesium3DTileset.ConstructorOptions): Promise<Cesium3DTileset>;

[cesium-concierge]

Thank you so much for the pull request @angrycat9000! I noticed this is your first pull request and I wanted to say welcome to the Cesium community!

The Pull Request Guidelines is a handy reference for making sure your PR gets accepted quickly, so make sure to skim that.

• ❌ Missing CONTRIBUTORS.md entry.
  • Please add yourself to the contributors file!
• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.

[angrycat9000]

Updated with that suggestion @ggetz

[ggetz]

Great, thanks @angrycat9000 !