Adding missing semicolon in two C# code samples

[captainbrosset]

Rendered article sections for review:

• https://review.learn.microsoft.com/microsoft-edge/webview2/how-to/context-menus?branch=pr-en-us-3009&tabs=csharp#example-adding-custom-menu-items-to-a-default-context-menu
• https://review.learn.microsoft.com/microsoft-edge/webview2/how-to/webresourcerequested?branch=pr-en-us-3009&tabs=dotnet#example-intercepting-a-request-to-monitor-or-modify-it

This PR fixes #3008.

I don't know C# myself, but every other examples of delegate usage in the repo, and on github seems to also require a semi-colon.

AB#48412538

[learn-build-service-prod]

Learn Build status updates of commit 4c8119a:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-edge/webview2/how-to/context-menus.md	✅Succeeded	View
microsoft-edge/webview2/how-to/webresourcerequested.md	✅Succeeded	View

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