[rand.req.dist] fix grammar typo

Author: jwakely

source/numerics.tex

@@ -2355,7 +2355,7 @@
 \tcode{os << d}
 or of
 any \keyword{const} member function of \tcode{D}
-between any of the invocations \tcode{d(g)}.
+between any of the invocations of \tcode{d(g)}.
 
 \pnum
 If a textual representation is written using \tcode{os << x}