Fix flaky project import spec

What does this MR do?

Fixes project import spec by not relying in the flash banner and instead waiting on "Import in progress" to go away.

Related to: #211528 (comment 356415066)

Conformity

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