Security sprint: Update content that features the ROPC Flow

[Dickson-Mwendia]

This PR updates content that features the ROPC flow and related issues identified in the MSAL.NET docset.

Cc: @SHERMANOUKO @CelesteDG

[learn-build-service-prod]

Learn Build status updates of commit b8c1ef1:

✅ Validation status: passed

File	Status	Preview URL	Details
msal-dotnet-articles/acquiring-tokens/desktop-mobile/adfs-support.md	✅Succeeded	View
msal-dotnet-articles/acquiring-tokens/desktop-mobile/social-identities.md	✅Succeeded	View
msal-dotnet-articles/acquiring-tokens/desktop-mobile/wam.md	✅Succeeded	View
msal-dotnet-articles/acquiring-tokens/overview.md	✅Succeeded	View
msal-dotnet-articles/advanced/testing-apps-using-msal.md	✅Succeeded	View
msal-dotnet-articles/getting-started/scenarios.md	✅Succeeded	View
msal-dotnet-articles/how-to/migrate-public-client.md	✅Succeeded	View
msal-dotnet-articles/how-to/token-cache-serialization.md	✅Succeeded	View
msal-dotnet-articles/resources/handling-pii.md	✅Succeeded	View

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[Dickson-Mwendia]

@localden Not related to the updates in this PR, but I see a couple of broken links from the Link Checker run results summary, which I'll go ahead and fix.

A quick look shows that they're stemming from a recently archived sample - https://github.com/Azure-Samples/active-directory-dotnet-v1-to-v2. I'd prefer not pointing to an archived repo, but I can't seem to find a more recent sample that demos migration from ADAL to MSAL.