`InstanceNotFoundError` is not documented

### Description of the modifications

All the exceptions are documented except this one in the API reference: https://pypim.docs.pyansys.com/api/index.html

### Useful links and references

_No response_

Open the API reference linked in the issue and locate how the other exceptions are included in the generated documentation. Find the definition or documentation entry for InstanceNotFoundError, add the missing API reference entry, and verify that the exception appears alongside the other documented exceptions.

Written by the indexing model from the issue text.