Update csharp-netcore dependencies to the latest stable version

[wing328]

• Update csharp-netcore dependencies to the latest stable version
• Fix code due to change in method signature in the newer version of the dependencies.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• If contributing template-only or documentation-only changes which will change sample output, build the project beforehand.
• Run the shell script ./bin/generate-samples.shto update all Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language.

cc @mandrean (2017/08) @frankyjuang (2019/09) @shibayan (2020/02)

[shibayan]

I have checked the package dependencies. LGTM

[wing328]

Upgraded CompareNETObjects to 4.61.0 instead of the latest version 4.66.0, which results in the following errors in the CI:

dotnet test samples\client\petstore\csharp-netcore\OpenAPIClient\src\Org.OpenAPITools.Test\Org.OpenAPITools.Test.csproj
Test run for C:\projects\openapi-generator\samples\client\petstore\csharp-netcore\OpenAPIClient\src\Org.OpenAPITools.Test\bin\Debug\netcoreapp2.0\Org.OpenAPITools.Test.dll(.NETCoreApp,Version=v2.0)
Microsoft (R) Test Execution Command Line Tool Version 16.2.0-preview-20190606-02
Copyright (c) Microsoft Corporation.  All rights reserved.
Starting test execution, please wait...
The active test run was aborted. Reason: Test host process crashed : Process is terminating due to StackOverflowException.
Test Run Aborted.
Total tests: Unknown
     Passed: 152
 Total time: 9.4195 Seconds
Command exited with code 1