Trivial formatting issue

CONTRIBUTING.rst

@@ -22,6 +22,7 @@ in log_level=0, and include the relevant logs in your bug report.
 
 If the issue you’re reporting may have security implications, please
 select the “confidential” flag in your bug report. This includes, but is not limited to:
+
 - disclosure of private data that was supposed to be encrypted using TLS
 - denial of service (crash, infinite loop, etc) that can be caused by any
   user