fix(revert): element(locator).then should not appear in the docs and change reverted. (#3808)

- change comments to not be in JSDoc format
- reverts change `element(locator).then`

Author: cnishina

lib/element.ts

@@ -787,21 +787,7 @@ export class ElementArrayFinder extends WebdriverWebElement {
 export class ElementFinder extends WebdriverWebElement {
   parentElementArrayFinder: ElementArrayFinder;
   elementArrayFinder_: ElementArrayFinder;
-
-  /**
-   * Access the underlying actionResult of ElementFinder.
-   *
-   * @alias element(locator).then(thenFunction)
-   * @param {function(webdriver.promise.Promise)} fn Function which takes
-   *     the value of the underlying actionResult.
-   * @param {function(Error)} errorFn
-   *
-   * @returns {webdriver.promise.Promise} Promise which contains the results
-   * of evaluating fn.
-   */
-  then(fn: Function, errorFn?: Function): wdpromise.Promise<any> {
-    return null;
-  }
+  then: (fn: Function, errorFn?: Function) => wdpromise.Promise<any> = null;
 
   constructor(public browser_: ProtractorBrowser, elementArrayFinder: ElementArrayFinder) {
     super();
@@ -813,6 +799,7 @@ export class ElementFinder extends WebdriverWebElement {
     // Only have a `then` method if the parent element array finder
     // has action results.
     if (this.parentElementArrayFinder.actionResults_) {
+      // Access the underlying actionResult of ElementFinder.
       this.then =
           (fn: (value: any) => {} | wdpromise.IThenable<{}>, errorFn?: (error: any) => any) => {
             return this.elementArrayFinder_.then((actionResults: any) => {