Bump MSAL dependencies to 4.86.1 in central props

[Copilot]

This PR updates the existing bump-msal-4.86.1 branch for master by moving Microsoft Identity Client dependencies from 4.86.0 to 4.86.1. Scope is intentionally limited to the central version properties used across the solution.

• Dependency version update

  • Directory.Build.props now pins:
    • MicrosoftIdentityClientVersion → 4.86.1
    • MicrosoftIdentityClientKeyAttestationVersion → 4.86.1

• Compatibility intent

  • No code-path changes were introduced; this is a package-version-only bump to consume the latest MSAL patch release while preserving existing behavior.

<PropertyGroup Label="Common dependency versions">
  <MicrosoftIdentityClientVersion Condition="'$(MicrosoftIdentityClientVersion)' == ''">4.86.1</MicrosoftIdentityClientVersion>
  <MicrosoftIdentityClientKeyAttestationVersion Condition="'$(MicrosoftIdentityClientKeyAttestationVersion)' == ''">4.86.1</MicrosoftIdentityClientKeyAttestationVersion>
</PropertyGroup>

[neha-bhargava]

There is a dependabot created PR as well