[csharp] Update restsharp to the latest stable version

[ondrej-krc-jediny]

Update RestSharp to the latest stable version (111.4.1). The version 110.2.0 used currently has a dependency on System.Text.Json 7.0.2, which is vulnerable with high severity. The latest stable version 111.4.1 depends on System.Text.Json 8.0.4, that is not vulnerable.

[wing328]

thanks for opening a ticket/issue on this

would you like to contribute a PR to update the version to the latest?

a good reference PR is https://github.com/OpenAPITools/openapi-generator/pull/16122

[jacobilsoe]

I think it should be upgraded to 1.112.0 since older versions are vulnerable.

[jacobilsoe]

Thank you @wing328