Fix missing period in docstring

Author: snitish

pandas/core/window/expanding.py

@@ -674,7 +674,7 @@ def kurt(self, numeric_only: bool = False):
         dedent(
             """
         GroupBy.first : Similar method for GroupBy objects
-        Expanding.last : Method to get the last element in each window\n
+        Expanding.last : Method to get the last element in each window.\n
         """
         ).replace("\n", "", 1),
         create_section_header("Examples"),
@@ -710,7 +710,7 @@ def first(self, numeric_only: bool = False):
         dedent(
             """
         GroupBy.last : Similar method for GroupBy objects
-        Expanding.first : Method to get the first element in each window\n
+        Expanding.first : Method to get the first element in each window.\n
         """
         ).replace("\n", "", 1),
         create_section_header("Examples"),

pandas/core/window/rolling.py

@@ -2565,7 +2565,7 @@ def kurt(self, numeric_only: bool = False):
         dedent(
             """
         GroupBy.first : Similar method for GroupBy objects
-        Rolling.last : Method to get the last element in each window\n
+        Rolling.last : Method to get the last element in each window.\n
         """
         ).replace("\n", "", 1),
         create_section_header("Examples"),
@@ -2601,7 +2601,7 @@ def first(self, numeric_only: bool = False):
         dedent(
             """
         GroupBy.last : Similar method for GroupBy objects
-        Rolling.first : Method to get the first element in each window\n
+        Rolling.first : Method to get the first element in each window.\n
         """
         ).replace("\n", "", 1),
         create_section_header("Examples"),