_py/path: tiny change to `ensure` to silence EncodingWarning

We're not supposed to diverge here, but make this change to fix an
unavoidable EncodingWarning that is otherwise raised in pytest's test
suite. The behavior should be exactly the same besides the warning,
hopefully that won't cause confusion.

src/_pytest/_py/path.py

@@ -953,7 +953,7 @@ class LocalPath:
         else:
             p.dirpath()._ensuredirs()
             if not p.check(file=1):
-                p.open("w").close()
+                p.open("wb").close()
             return p
 
     @overload