Update dependencies to 4.3.0.

This makes the required versions consistent across all target frameworks.

Updating System.Runtime.InteropServices.RuntimeInformation to 4.3.0 was necessary for `dotnet xunit`.

It may help fix PomeloFoundation/Pomelo.EntityFrameworkCore.MySql#377

Author: bgrainger

src/MySqlConnector/MySqlConnector.csproj

@@ -21,9 +21,9 @@
   </PropertyGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net45' OR '$(TargetFramework)' == 'net46' ">
-    <PackageReference Include="System.Buffers" Version="4.0.0" />
-    <PackageReference Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.0.0" />
-    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.0.0" />
+    <PackageReference Include="System.Buffers" Version="4.3.0" />
+    <PackageReference Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.3.0" />
     <Reference Include="System.Data" />
     <Reference Include="System.Transactions" />
   </ItemGroup>