[expr.unary.op] Say "the ~ operator" consistently, remove "unary"

We are currently using the term "unary complement operator" to refer
to the "~" operator without ever giving it that name. This change
removes the use of that undefined term.

Author: burblebee

source/expressions.tex

@@ -4664,7 +4664,7 @@
 
 \pnum
 \indextext{operator!ones' complement}%
-The operand of \tcode{\~{}} shall have integral or unscoped enumeration type.
+The operand of the \tcode{\~{}} operator shall have integral or unscoped enumeration type.
 Integral promotions are performed.
 The type of the result is the type of the promoted operand.
 % FIXME: [basic.fundamental]/p5 uses $x_i$; [expr] uses $\tcode{x}_i$.
@@ -4677,7 +4677,7 @@
 There is an ambiguity
 in the grammar when \tcode{\~{}} is followed by
 a \grammarterm{type-name} or \grammarterm{decltype-specifier}.
-The ambiguity is resolved by treating \tcode{\~{}} as the unary complement
+The ambiguity is resolved by treating \tcode{\~{}} as the
 operator rather than as the start of an \grammarterm{unqualified-id}
 naming a destructor.
 \begin{note}