Bump MimeKit from 4.3.0 to 4.7.1 in /src/Yavsc.Server

Bumps [MimeKit](https://github.com/jstedfast/MimeKit) from 4.3.0 to 4.7.1.
- [Changelog](https://github.com/jstedfast/MimeKit/blob/master/ReleaseNotes.md)
- [Commits](https://github.com/jstedfast/MimeKit/compare/4.3.0...4.7.1)

---
updated-dependencies:
- dependency-name: MimeKit
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

src/Yavsc.Server/Yavsc.Server.csproj

@@ -23,7 +23,7 @@
     <PackageReference Include="SixLabors.ImageSharp" Version="3.1.6" />
     <PackageReference Include="RazorEngine.NetCore" Version="3.1.0" />
     <PackageReference Include="MailKit" Version="4.3.0" />
-    <PackageReference Include="MimeKit" Version="4.3.0" />
+    <PackageReference Include="MimeKit" Version="4.7.1" />
     <PackageReference Include="pazof.rules" Version="1.1.3" />
   </ItemGroup>
   <ItemGroup>