Apply ruff/Pylint rule PLC0208

PLC0208 Use a sequence type instead of a `set` when iterating over values

Author: DimitriPapadopoulos

tests/test_base.py

@@ -834,7 +834,7 @@ def test_loop_call_later_handle_cancelled(self):
 
     def test_loop_std_files_cloexec(self):
         # See https://github.com/MagicStack/uvloop/issues/40 for details.
-        for fd in {0, 1, 2}:
+        for fd in (0, 1, 2):
             flags = fcntl.fcntl(fd, fcntl.F_GETFD)
             self.assertFalse(flags & fcntl.FD_CLOEXEC)