Remove https from Snowplow Collector URI placeholder in Admin Area

What does this MR do?

Remove https from Snowplow Collector URI placeholder in Admin Area. Protocol is configured using the forceSecureTracker option during tracker initialization and is enforced anyway.

Discussed at https://gitlab.com/gitlab-com/infrastructure/issues/4731#note_93827442

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/6336

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?