CONTRIBUTING.md: remove overly harsh msg

Inspired by this past commit[1], we should continue to be
less and less harsh in our docs.

[1] cb686b5

Author: knocte

CONTRIBUTING.md

@@ -11,8 +11,6 @@ Use the issues tracker for:
 * [feature requests](#feature-requests)
 * [submitting pull requests](#pull-requests)
 
-Please **do not** use the issue tracker for personal or commercial support requests.
-
 ## Bug reports
 
 A bug is either a _demonstrable problem_ that is caused by the code in the repository,