Closes #451 - Add pragma restore directive for the CS0108 warning

[GabrieleMessina]

Closes #451

I've added a pragma restore directive for the CS0108 warning into the ObservableObject class source generator.

I haven't updated the tests to support the newly generated code yet. I want to be sure this can be a good solution before proceeding to that seeing that updating the test is a lot of work.
@Sergio0694 Can you confirm I can proceed?

PR Checklist

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• Tested code with current supported SDKs
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Code follows all style conventions

Other information

I've not found a way of testing the newly generated code on an actual class that inherits from ObservableObject.
When I try to add this kind of class nothing goes generated under the hood. There is a way of testing this like I'm working with the final nuget package?