Remove obsolete logic from pdfjs-init
Remove obsolete logic from pdfjs-init

 - Remove the `eventBusDispatchToDOM` option, as the client now watches
   for these events on the event bus. See [1].
 - Use `PDFViewerApplication.initializedPromise` to simplify waiting for
   app to load. This was added in PDF.js v2.10.377. See [2].

[1] https://github.com/hypothesis/client/pull/2641
[2] https://github.com/mozilla/pdf.js/pull/11607

hypothesis/browser-extension,hypothesis/browser-extension,hypothesis/browser-extension,hypothesis/browser-extension