Fixing docstring order (and test because NaT and Timestamp docstring did not match)

Author: datapythonista

pandas/_libs/tslibs/nattype.pyx

@@ -471,10 +471,6 @@ class NaTType(_NaT):
         """
         Round the Timestamp to the specified resolution
 
-        Returns
-        -------
-        a new Timestamp rounded to the given resolution of `freq`
-
         Parameters
         ----------
         freq : a freq string indicating the rounding resolution
@@ -497,6 +493,10 @@ class NaTType(_NaT):
 
             .. versionadded:: 0.24.0
 
+        Returns
+        -------
+        a new Timestamp rounded to the given resolution of `freq`
+
         Raises
         ------
         ValueError if the freq cannot be converted