Attempt to simplify the fileattachmentannotation event dispatching

This attempts to reduced the level of indirection, and the amount of code, when dispatching `fileattachmentannotation` events, by removing the `PDFLinkService.onFileAttachmentAnnotation` method and just accessing `PDFLinkService.eventBus` directly in the `FileAttachmentAnnotationElement` constructor.
Given that other properties, such as `externalLinkTarget`/`externalLinkRel`, are already being accessed directly this pattern seems fine here as well.

web/interfaces.js

@@ -67,11 +67,6 @@ class IPDFLinkService {
    */
   executeNamedAction(action) {}
 
-  /**
-   * @param {Object} params
-   */
-  onFileAttachmentAnnotation({ id, filename, content, }) {}
-
   /**
    * @param {number} pageNum - page number.
    * @param {Object} pageRef - reference to the page.