Don't return filename from upload

The uploader only needs to return the object_name of the uploaded
object. The filename is read directly from the input, so there's no need
to return it as well.

tests/models/test_attachment.py

@@ -9,6 +9,7 @@ from tests.mocks import PDF_FILENAME
 def test_attach(pdf_upload):
     attachment = Attachment.attach(pdf_upload)
     assert attachment.filename == PDF_FILENAME
+    assert attachment.object_name is not None
 
 
 def test_attach_raises():

tests/test_uploader.py

@@ -21,8 +21,7 @@ NONPDF_FILENAME = "tests/fixtures/disa-pki.html"
 
 
 def test_upload(uploader, upload_dir, pdf_upload):
-    filename, object_name = uploader.upload(pdf_upload)
-    assert filename == PDF_FILENAME
+    object_name = uploader.upload(pdf_upload)
     assert os.path.isfile(os.path.join(upload_dir, object_name))