DOC: fix broken link in "What is NumPy?" to broadcasting

Author: hkennyv

doc/source/user/whatisnumpy.rst

@@ -125,7 +125,7 @@ same shape, or a scalar and an array, or even two arrays of with
 different shapes, provided that the smaller array is "expandable" to
 the shape of the larger in such a way that the resulting broadcast is
 unambiguous. For detailed "rules" of broadcasting see
-`basics.broadcasting`.
+:ref:`Broadcasting <basics.broadcasting>`.
 
 Who Else Uses NumPy?
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