Actually test the file: prefix. (#3401)

Remove the mistaken conditional check from an apparent vestigial
thought-process during initial implementation.

parsl/tests/unit/test_file.py

@@ -78,7 +78,7 @@ def test_file_repr(scheme):
     netloc = "some.netloc"
     filename = "some_file_name"
     path = f"/some/path/{filename}"
-    if scheme and scheme != "file":
+    if scheme:
         url = f"{scheme}://{netloc}{path}"
     else:
         scheme = "file"