Bump MailKit from 4.2.0 to 4.3.0

Bumps [MailKit](https://github.com/jstedfast/MailKit) from 4.2.0 to 4.3.0.
- [Changelog](https://github.com/jstedfast/MailKit/blob/master/ReleaseNotes.md)
- [Commits](jstedfast/MailKit@4.2.0...4.3.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

DigitalLearningSolutions.Data/DigitalLearningSolutions.Data.csproj

@@ -14,7 +14,7 @@
     <PackageReference Include="Dapper" Version="2.1.15" />
     <PackageReference Include="Dapper.FluentMap" Version="2.0.0" />
     <PackageReference Include="FuzzySharp" Version="2.0.2" />
-    <PackageReference Include="MailKit" Version="4.2.0" />
+    <PackageReference Include="MailKit" Version="4.3.0" />
     <PackageReference Include="Microsoft.FeatureManagement.AspNetCore" Version="2.0.0" />
     <PackageReference Include="Serilog.AspNetCore" Version="7.0.0" />
     <PackageReference Include="System.Drawing.Common" Version="7.0.0" />