acc: docs - small fix to cdr_extra param example

src/modules/acc/doc/acc_admin.xml

@@ -1156,7 +1156,7 @@ modparam("acc", "cdr_facility", "LOG_DAEMON")
 		<title>cdr_extra example</title>
 		<programlisting format="linespecific">
 ...
-modparam("acc", "cdr_extra", "c1=$dlg_var(caller);c2=$dlg_var(callee)"
+modparam("acc", "cdr_extra", "c1=$dlg_var(caller);c2=$dlg_var(callee)")
 ...
 </programlisting>
 		</example>