Remove upcoming database deprecation warning

What does this MR do?

Per omnibus-gitlab#5499 (comment 387685215), this MR removes the upcoming database deprecation notice in favor of only displaying a message if the current database version minimum is not met.

Context: pros/cons of upcoming deprecation feature

• Pros:
  • Provides admins with advanced notice that is tailored to their specific version of the database
• Cons:
  • Can cause confusion to admins as the message looks very similar to the warning that the current database version requirement is not met (as opposed to the upcoming requirement)
  • Adds to the list of places to keep track of (and update) version information
  • Message will re-appear upon each load of the admin UI, even if the user previously dismissed the notice

Given the cons listed above, this MR proposes removing this feature pending feedback from the team.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team