Remove IIFEs from project_find_file.js

What does this MR do?

Replaces the 'Immediately Invoked Function Expression' from javascript function in 'keyup' event in the 'Find Project File' feature as requested in &2074 (closed) -> #34623 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

• Tested in all supported browsers