Update integrating-services-with-a-property-editor.md

[grayn90]

Description

• Replace UmbPropertyEditorExtensionElement with UmbPropertyEditorUiElement in the extension-registry import.
• Update import modal context and modal open logic to use the UmbModalTokenDefaults in modal-token.d.ts as the args.
• Replace usages of _notificationContext with #notifcationContext. This should probably be aligned between part 3 and part 4 of this tutorial as part 3 uses _notificationContext syntax and part 4 uses #notificationContext.

Type of suggestion

• Typo/grammar fix
• Updated outdated content
• New content
• Updates related to a new version
• Other

Product & version (if relevant)

v14.0.0-rc2

Deadline (if relevant)

When should the content be published?

[alina-tincas]

Hi @grayn90 thank you for the PR #h5YR

All looks good so I will merge this PR once your previous PR is merged 💪