DOC: Fix SS03 docstring error (#30939)

xref:

#27977
#30733

Author: galuhsahid

pandas/core/arrays/datetimelike.py

@@ -920,7 +920,7 @@ def freq(self, value):
     @property
     def freqstr(self):
         """
-        Return the frequency object as a string if its set, otherwise None
+        Return the frequency object as a string if its set, otherwise None.
         """
         if self.freq is None:
             return None

pandas/core/window/indexers.py

@@ -32,7 +32,7 @@
 
 
 class BaseIndexer:
-    """Base class for window bounds calculations"""
+    """Base class for window bounds calculations."""
 
     def __init__(
         self, index_array: Optional[np.ndarray] = None, window_size: int = 0, **kwargs,