Fix the remaining Promise.resolve(undefined) cases

Many years ago now there were some `Promise` implementations that had issues resolving with an *implicitly* `undefined` value. That should no longer be the case, and we've not been using the `Promise.resolve(undefined)` format for a long time, hence this patch fixes the few remaining cases.

web/pdf_page_view.js

@@ -831,7 +831,7 @@ class PDFPageView {
     renderTask.promise.then(
       function () {
         showCanvas();
-        renderCapability.resolve(undefined);
+        renderCapability.resolve();
       },
       function (error) {
         showCanvas();

web/pdf_thumbnail_view.js

@@ -278,7 +278,7 @@ class PDFThumbnailView {
   draw() {
     if (this.renderingState !== RenderingStates.INITIAL) {
       console.error("Must be in new state before drawing");
-      return Promise.resolve(undefined);
+      return Promise.resolve();
     }
     const { pdfPage } = this;