Update outdated statement from math about C standard (python#134621)

Co-authored-by: Adam Turner <[email protected]>

Author: hugovk

Doc/library/math.rst

@@ -10,8 +10,8 @@
 
 --------------
 
-This module provides access to the mathematical functions defined by the C
-standard.
+This module provides access to common mathematical functions and constants,
+including those defined by the C standard.
 
 These functions cannot be used with complex numbers; use the functions of the
 same name from the :mod:`cmath` module if you require support for complex