feat: Adds new feature flag back_button_support

[elikmiller]

Description

Describe your changes in detail

• Adds a new disabled, non-user updatable feature flag back_button_support to the feature_flags table

Motivation and Context

This PR addresses: BED-5438

Why is this change required? What problem does it solve?

This feature flag enables developers to begin building out support for BED-4757 (also #781) without impacting end users.

How Has This Been Tested?

No tests have been added or modified. This change contains only an updated migration file to update records in the postgres database.

Please describe in detail how you tested your changes.
Include details of your testing environment, and the tests you ran to
see how your change affects other areas of the code, etc.

Screenshots (optional):

No screenshots.

Types of changes

• Database Migrations

Checklist:

• I have met the contributing prerequisites
  • Assigned myself to this PR
  • Added the appropriate labels
  • Associated an issue: Issues and Pull Requests README #672
  • Read the Contributing guide: https://github.com/SpecterOps/BloodHound/wiki/Contributing
• I have ensured that related documentation is up-to-date
  • Open API docs
  • Code comments (GoDocs / JSDocs)
• I have followed proper test practices
  • Added/updated tests to cover my changes
  • All new and existing tests passed