add new target framework net461

[dmitryGolikov]

No description provided.

[DevExpressExampleBot]

Please correct the project and update this pull request by pushing a new commit.

C:\Program Files\dotnet\sdk\2.1.400\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.TargetFrameworkInference.targets(137,5): error NETSDK1045: The current .NET SDK does not support targeting .NET Core 4.5.2.  Either target .NET Core 2.1 or lower, or use a version of the .NET SDK that supports .NET Core 4.5.2. [R:\Temp\10b4c3f3-da95-4355-8e3c-8527741fc8e7\tempTestingCS\DXCustomConnectionStringsConfiguration\DXCustomConnectionStringsConfiguration.csproj]

http://codecentral:8080/job/How-to-add-connection-strings-from-custom-configuration-in-the-report-designer_18.2.3+/4/console