Fix docstring

Author: bang128

pandas/core/indexes/base.py

@@ -2258,7 +2258,7 @@ def is_boolean(self) -> bool:
         is_integer : Check if the Index only consists of integers (deprecated).
         is_floating : Check if the Index is a floating type (deprecated).
         is_numeric : Check if the Index only consists of numeric data.
-        is_object : Check if the Index is of the object dtype. (deprecated)
+        is_object : Check if the Index is of the object dtype (deprecated).
         is_categorical : Check if the Index holds categorical data.
         is_interval : Check if the Index holds Interval objects (deprecated).