Remove hashed storage req. for Design Management

What does this MR do?

This MR removes the hashed storage requirement for Design Management.

Hashed storage is now the only storage, so we can remove this requirement from Design Management.

• Issue: #35477 (closed)

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