Bump MailKit from 4.7.1.1 to 4.8.0 in /Framework (#282)

Bumps [MailKit](https://github.com/jstedfast/MailKit) from 4.7.1.1 to 4.8.0.
- [Changelog](https://github.com/jstedfast/MailKit/blob/master/ReleaseNotes.md)
- [Commits](jstedfast/MailKit@4.7.1.1...4.8.0)

---
updated-dependencies:
- dependency-name: MailKit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Troy Walsh <[email protected]>

Author: dependabot[bot]

Framework/BaseEmailTest/BaseEmailTest.csproj

@@ -47,7 +47,7 @@
 	</PropertyGroup>
 
 	<ItemGroup>
-		<PackageReference Include="MailKit" Version="4.7.1.1" />
+		<PackageReference Include="MailKit" Version="4.8.0" />
 		<PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0">
 			<PrivateAssets>all</PrivateAssets>
 			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>