CPP: QLDoc fix for Stmt.qll.

Author: geoffw0

cpp/ql/src/semmle/code/cpp/stmts/Stmt.qll

@@ -1645,6 +1645,7 @@ class EnumSwitch extends SwitchStmt {
  * } catch (std::exception &e) {
  *   g();
  * }
+ * ```
  * there is a handler that's associated with the `catch` block and controls
  * entry to it.
  */