unavailable "timeExample" V&V testcase

The documentation describes an example of various time schemes (ref. 1) with a link to a V&V testcase, timeExample (ref. 2). The specific case seem to be unavailable in the repository (when following the link I get error 404: The page could not be found or you don't have permission to view it.).

References:

1. https://openfoam.com/documentation/cpp-guide/html/guide-schemes-time-example.html
2. https://develop.openfoam.com/development/OpenFOAM-plus/tree/master/tutorials/verificationAndValidation/schemes/timeExample

## Reattaching the author to the issue ticket: @michele ##