[NGO Admin] Uploaded observers file list remains prefilled in upload modal

[overeha]

Summary:
After I import a file with observers the name of the last file uploaded remains in the modal.

Steps to reproduce:

1. Import an observers csv
2. Finalize process
3. Go back to Import observers
4. Click on "Import observers list"
   the name of the previously imported file is still in the Drag and Drop area (please see media)

This is very confusing as I am not sure if i can upload a new file again or i might try to reupload the same file.

System:
MacOS

[mirunaioana-msc]

@avasi-code4ro - please retest this