[native] Replace hacky call to imported dispatch in intentionalSaveMedia

Summary: While working on D5667, I noticed this hacky dispatch call, and figured it would be good to replace with something more idiomatic.

Test Plan: Test that saving an image from ImageModal still works and generates a report

Reviewers: atul, tomek

Reviewed By: atul

Differential Revision: https://phab.comm.dev/D5668