Drop unused import of xdist

Added in a4debd6 unnecessarily.

Author: adamchainz

src/pytest_randomly/__init__.py

@@ -18,11 +18,6 @@
 else:
     from importlib.metadata import entry_points
 
-try:
-    import xdist
-except ImportError:  # pragma: no cover
-    xdist = None
-
 # factory-boy
 try:
     from factory.random import set_random_state as factory_set_random_state