Add (some) optional chaining usage in src/display/api.js

Since we no longer use SystemJS to load the unit-tests, there's now nothing that prevents us from using optional chaining and nullish coalescing in the `src/display/` directory.

src/display/api.js

@@ -1168,8 +1168,7 @@ class PDFPageProxy {
         pageIndex: this._pageIndex,
         intent: renderingIntent,
         renderInteractiveForms: renderInteractiveForms === true,
-        annotationStorage:
-          (annotationStorage && annotationStorage.getAll()) || null,
+        annotationStorage: annotationStorage?.getAll() || null,
       });
     }
 
@@ -2551,8 +2550,7 @@ class WorkerTransport {
     return this.messageHandler
       .sendWithPromise("SaveDocument", {
         numPages: this._numPages,
-        annotationStorage:
-          (annotationStorage && annotationStorage.getAll()) || null,
+        annotationStorage: annotationStorage?.getAll() || null,
         filename: this._fullReader ? this._fullReader.filename : null,
       })
       .finally(() => {