[class.virtual] Add commas (#7062)

Author: Eisenwave

source/classes.tex

@@ -3705,13 +3705,13 @@
 determining overriding.
 \end{footnote}
 $F$.
-For convenience we say that any virtual function overrides itself.
+For convenience, we say that any virtual function overrides itself.
 \indextext{overrider!final}%
 A virtual member function $V$ of a class object $S$ is a \defn{final
 overrider} unless the most derived class\iref{intro.object} of which $S$ is a
 base class subobject (if any) has another member function that overrides $V$.
 In a derived class, if a virtual member function of a base class subobject
-has more than one final overrider the program is ill-formed.
+has more than one final overrider, the program is ill-formed.
 \begin{example}
 \begin{codeblock}
 struct A {