Update secret detection pattern entries

Add navigation item to global navigation

• Link to the merge request that introduced the new page: gitlab!161118 (merged)
• Give the MR a descriptive title.
• Optional. Link to the new page: https://docs.gitlab.com/ee/user/application_security/secret_detection/detected_secrets.html

Note:

The linked MR collated information from 3 separate pages into 1. To match those changes, this MR removes the original 3 navigation entries, replacing them with just 1 entry.