When you installed the ProBuilder runtime examples via Package Manger, the following warning appears in the console:

Component of type GUI Layer is no longer available in Unity. References to it will be removed!

The examples should be updated so they don't use this component.

1. Open Unity
2. Create a new project with any settings
3. Open Package Manager via Window > Package Manger
4. Find the ProBuilder package
5. Install ProBuilder if not installed
6. Install the Runtime Examples
7. Inspect the console

Expected Result:
No errors or warnings should appear in the console.

Actual Result:
When the examples are installed, a warning appears in the console.

Tested on Windows.

Occurs with package version 4.1.0 using 2019.3.0a10