Clarify the meaning of "since" and "to" parameters for api/qualityprofiles/changelog

The description of the since and to parameters for the api/qualityprofiles/changelog endpoint don't make it clear that the former is inclusive, and the latter exclusive

Suggestion:

since: Start date for the changelog (inclusive).
Either a date (server timezone) or datetime can be provided.

to: End date for the changelog (exclusive, strictly before).
Either a date (server timezone) or datetime can be provided.