DOC: Fix remove_unused_levels doctest on main (pandas-dev#57827)

Author: mroeschke

pandas/core/indexes/multi.py

@@ -2063,7 +2063,7 @@ def remove_unused_levels(self) -> MultiIndex:
 
         >>> mi2 = mi[2:].remove_unused_levels()
         >>> mi2.levels
-        (Index([1], dtype='int64'), Index(['a', 'b'], dtype='object'))
+        (RangeIndex(start=1, stop=2, step=1), Index(['a', 'b'], dtype='object'))
         """
         new_levels = []
         new_codes = []