Update dependency MongoDB.Driver to 3.9.0

Author: dependencyupdates[bot]

src/NServiceBus.Storage.MongoDB/NServiceBus.Storage.MongoDB.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="MongoDB.Driver" Version="3.8.1" />
+    <PackageReference Include="MongoDB.Driver" Version="3.9.0" />
     <PackageReference Include="NServiceBus" Version="10.2.4" />
     <PackageReference Include="Particular.Obsoletes" Version="1.1.0" PrivateAssets="All" ExcludeAssets="runtime" />
     <PackageReference Include="Particular.Packaging" Version="4.5.0" PrivateAssets="All" />