Draft: Include CE/EE hint in "version mismatch" error

What does this MR do?

When users upgrade from CE to EE and want to import a CE backup, the resulting error message does not make it clear, that

according to the backup and restore docu "exactly the same version and type" are required:

Your current GitLab version (X.Y.Z-ee) differs from the GitLab version in the backup!
Please switch to the following version and try again:
version: X.Y.Z

CE or -ce are not mentioned, because CE doesn't use that VERSION suffix.

An alternative to this text change might be a code change that explicitely checks the type as well.

Screenshots

See ZD ticket (internal) for context.

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