change the indent for the pydoc of apply() function. (pandas-dev#20715)

pandas/core/series.py

@@ -3130,7 +3130,7 @@ def apply(self, func, convert_dtype=True, args=(), **kwds):
         >>> def add_custom_values(x, **kwargs):
         ...     for month in kwargs:
         ...         x+=kwargs[month]
-        ...         return x
+        ...     return x
 
         >>> series.apply(add_custom_values, june=30, july=20, august=25)
         London      95