[meta.reflection.queries] Add comma in comment in example (cplusplus#9020)

Author: Andreas-Krug

source/meta.tex

@@ -3913,7 +3913,7 @@
 int x;
 int& y = x;
 
-static_assert(^^x != ^^y);                          // OK, \tcode{r} and \tcode{y} are different variables so their
+static_assert(^^x != ^^y);                          // OK, \tcode{r} and \tcode{y} are different variables, so their
                                                     // reflections compare different
 static_assert(object_of(^^x) == object_of(^^y));    // OK, because \tcode{y} is a reference
                                                     // to \tcode{x}, their underlying objects are the same