[func.wrap.{func.general, move.class}] Remove 'first-class object' (#5067)

The term is undefined and does not improve the specification.

Author: jensmaurer

source/utilities.tex

@@ -16113,7 +16113,7 @@
 The \tcode{function} class template provides polymorphic wrappers that
 generalize the notion of a function pointer. Wrappers can store, copy,
 and call arbitrary callable objects\iref{func.def}, given a call
-signature\iref{func.def}, allowing functions to be first-class objects.
+signature\iref{func.def}.
 
 \pnum
 \indextext{callable type}%
@@ -16571,7 +16571,7 @@
 The \tcode{move_only_function} class template provides polymorphic wrappers
 that generalize the notion of a callable object\iref{func.def}.
 These wrappers can store, move, and call arbitrary callable objects,
-given a call signature, allowing functions to be first-class objects.
+given a call signature.
 
 \pnum
 \recommended