Remove modelFilesConstrainedTo from gradle example

[feenr]

Updated the gradle example to exclude the modelFilesConstrainedTo parameter.

I didn't do any testing beyond using this same configuration when trying out the openapi-generator project. The parameter is optional, and ommitting it should not cause any negative behaviors for new users.

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[wing328]

@feenr thanks for the PR. Is modelFilesConstrainedTo causing any issues to you?

[feenr]

@wing328 modelFilesConstrainedTo itself is working perfectly fine me. However, my first time using OpenAPIGenerator I copied the example from the readme, being unfamiliar with the settings. This results in a task run that is successful but has absoluately no output. It took some time to realize that modelFilesConstrainedTo was the root cause. I believe ommitting it from the example is a better onboarding experience for new users. As the user's usage of OpenAPI Generater gets more sophisticated they can choose to use modelFilesConstrainedTo to limit the generated output.

[feenr]

I created an issue outlining my reasoning.
#8311

[wing328]

@feenr thanks for the explanation and the PR to improve the example.