Consistently use @returns for returned data types in JSDoc comments

Sometimes we also used `@return`, but `@returns` is what the JSDoc
documentation recommends. Even though `@return` works as an alias, it's
good to use the recommended syntax and to be consistent within the
project.

src/shared/message_handler.js

@@ -177,7 +177,7 @@ MessageHandler.prototype = {
    * @param {Object} queueingStrategy - Strategy to signal backpressure based on
    *                 internal queue.
    * @param {Array} [transfers] - List of transfers/ArrayBuffers.
-   * @return {ReadableStream} ReadableStream to read data in chunks.
+   * @returns {ReadableStream} ReadableStream to read data in chunks.
    */
   sendWithStream(actionName, data, queueingStrategy, transfers) {
     let streamId = this.streamId++;