Fix documentation of Modifier.qll

Author: smowton

java/ql/src/semmle/code/java/Modifier.qll

@@ -18,7 +18,9 @@ abstract class Modifiable extends Element {
    * Holds if this element has modifier `m`.
    *
    * For most purposes, the more specialized predicates `isAbstract`, `isPublic`, etc.
-   * should be used, which also take implicit modifiers into account.
+   * should be used.
+   *
+   * Both this method and those specialized predicates take implicit modifiers into account.
    * For instance, non-default instance methods in interfaces are implicitly
    * abstract, so `isAbstract()` will hold for them even if `hasModifier("abstract")`
    * does not.