[concept.boolean] Reword satisfaction rules for Boolean to make them not

appear to depend on the "given" lvalues b1 and b2.

Author: zygoloid

source/concepts.tex

@@ -800,9 +800,9 @@
 \end{itemdecl}
 
 \pnum
-Given lvalues \tcode{b1} and \tcode{b2} of type
-\tcode{const remove_reference_t<B>},
-then \tcode{\libconcept{Boolean}<B>} is satisfied only if
+Let \tcode{b1} and \tcode{b2} be lvalues of type
+\tcode{const remove_reference_t<B>}.
+\tcode{\libconcept{Boolean}<B>} is satisfied only if
 
 \begin{itemize}
 \item \tcode{bool(b1) == !bool(!b1)}.