DOC: Updated applymap docstring (#53132)

Updated applymap docstring

Author: Rajasvi

pandas/io/formats/style.py

@@ -2051,7 +2051,7 @@ def applymap(
 
         .. deprecated:: 2.1.0
 
-           Styler.applymap_index has been deprecated. Use Styler.map_index instead.
+           Styler.applymap has been deprecated. Use Styler.map instead.
 
         Parameters
         ----------