[Security Solution] Remove exceptions_list, author and license from Diffable Rule

[jpdjere]

Resolves: elastic#196213

Summary

Excludes the fields exceptions_list, author and license from the DiffableRule definition.

This will:

• prevent them from appearing in the Three Way Diff component
• prevent them from being able to be passed as a value in the fields object of the /upgrade/_perform endpoint to set a specific pick_version for it (NOTE: the current logic already forces exceptions_list to upgrade to the CURRENT version, but removing it from DiffableRule, will completely remove the from the payload schema, and the endpoint will then throw a validation error if included, rather than silently ignoring it)

For maintainers

• This was checked for breaking API changes and was labeled appropriately