Downgrade connector further because it's broken

Author: peppy

Diff for: osu.Server.QueueProcessor/osu.Server.QueueProcessor.csproj

@@ -12,7 +12,7 @@
 
     <ItemGroup>
       <PackageReference Include="DogStatsD-CSharp-Client" Version="8.0.0" />
-      <PackageReference Include="MySqlConnector" Version="2.3.7" />
+      <PackageReference Include="MySqlConnector" Version="2.1.6" />
       <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
       <PackageReference Include="Sentry" Version="4.5.0" />
       <PackageReference Include="ppy.osu.Framework" Version="2024.329.0" />