Remove unnecessary complex condition for submit

What does this MR do?

As gitlab-ui#575 (closed) is fixed, there is no need a check if we should @submit in the search component.

Screenshots

The button is already disabled, so the external component doesn't have to do the check:

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

Related to #201733 (closed)