Reflect change in argument name

`filename_or_fp` was changed to `path_or_file` here:
https://github.com/pallets/flask/pull/3828/files#diff-1f51c8ded4d4ff7e13badab599ef22436c529c2b5f9c25dc6250c1f9fd985440R479

app/main/views/notifications.py

@@ -230,7 +230,7 @@ def view_letter_notification_as_preview(
     mimetype = 'image/png' if filetype == 'png' else 'application/pdf'
 
     return send_file(
-        filename_or_fp=file,
+        path_or_file=file,
         mimetype=mimetype,
     )
 

app/main/views/uploads.py

@@ -584,7 +584,7 @@ def delete_contact_list(service_id, contact_list_id):
 def download_contact_list(service_id, contact_list_id):
     contact_list = ContactList.from_id(contact_list_id, service_id=service_id)
     return send_file(
-        filename_or_fp=BytesIO(contact_list.contents.encode('utf-8')),
+        path_or_file=BytesIO(contact_list.contents.encode('utf-8')),
         attachment_filename=contact_list.saved_file_name,
         as_attachment=True,
     )

app/s3_client/s3_mou_client.py

@@ -13,7 +13,7 @@ def get_mou(organisation_is_crown):
     try:
         key = get_s3_object(bucket, filename)
         return {
-            'filename_or_fp': key.get()['Body'],
+            'path_or_file': key.get()['Body'],
             'attachment_filename': attachment_filename,
             'as_attachment': True,
         }