C++: Make it clear that 'getAnAssignment' also gets the expression from the initializer.

cpp/ql/lib/semmle/code/cpp/Variable.qll

@@ -140,7 +140,8 @@ class Variable extends Declaration, @variable {
    * This does _not_ include the initialization of the variable. Use
    * `Variable.getInitializer()` to get the variable's initializer,
    * or use `Variable.getAnAssignedValue()` to get an expression that
-   * is assigned to this variable somewhere in the program.
+   * is the right-hand side of an assignment or an initialization of
+   * the varible.
    */
   Assignment getAnAssignment() { result.getLValue() = this.getAnAccess() }