Update source/concepts.tex

Co-authored-by: Jonathan Wakely <[email protected]>

Author: tkoeppe

source/concepts.tex

@@ -833,7 +833,7 @@
 \begin{itemdescr}
 \pnum
 If \tcode{T} is an object type, then let \tcode{v} be an lvalue of type
-\tcode{T} or \tcode{\keyword{const} T} or an rvalue of type \tcode{const T}.
+\tcode{T} or \tcode{\keyword{const} T} or an rvalue of type \tcode{\keyword{const} T}.
 \tcode{T} models \libconcept{copy_constructible} only if
 
 \begin{itemize}