Merge branch 'gsd-confidence-filter-ce' into 'master'

Adds the CE port for the confidence filter

See merge request gitlab-org/gitlab-ce!28410

Author: axilleas

doc/user/application_security/security_dashboard/index.md

@@ -54,6 +54,7 @@ First, navigate to the Security Dashboard found under your group's
 Once you're on the dashboard, at the top you should see a series of filters for:
 
 - Severity
+- Confidence
 - Report type
 - Project