Update JetBrains.Annotations to 2020.3.0.

src/Discord.Net.Examples/Discord.Net.Examples.csproj

@@ -16,7 +16,7 @@
   <ItemGroup>
     <ProjectReference Include="..\Discord.Net.Core\Discord.Net.Core.csproj" />
     <ProjectReference Include="..\Discord.Net.WebSocket\Discord.Net.WebSocket.csproj" />
-    <PackageReference Include="JetBrains.Annotations" Version="2020.1.0" />
+    <PackageReference Include="JetBrains.Annotations" Version="2020.3.0" />
   </ItemGroup>
 
 </Project>