Update dependency MongoDB.Driver to 3.4.3 (#793)

Co-authored-by: dependencyupdates[bot] <218638057+dependencyupdates[bot]@users.noreply.github.com>

Author: dependencyupdates[bot]

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

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="MongoDB.Driver" Version="3.4.2" />
+    <PackageReference Include="MongoDB.Driver" Version="3.4.3" />
     <PackageReference Include="NServiceBus" Version="10.0.0-alpha.2" />
     <PackageReference Include="Particular.Packaging" Version="4.5.0" PrivateAssets="All" />
   </ItemGroup>