Update browser.contexts to browser.context

We've made a change which means that there is now a 1-to-1 mapping
between browser and a browserContext. This means that there can only
ever be one browserContext open at any given point per browser. So
the contexts method on browser now only needs to return the current
browserContext.

Author: ankur22

src/data/markdown/docs/02 javascript api/07 k6-experimental/01 browser.md

@@ -35,7 +35,7 @@ The browser module is the entry point for all your tests, and it is what interac
 
 | Method                                                                                    | Description                                                                                                                                           |
 |-------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------|
-| [browser.contexts()](/javascript-api/k6-experimental/browser/contexts)                        | Lets you access all open [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/)s.                                                        |
+| [browser.context()](/javascript-api/k6-experimental/browser/contexts)                        | Returns the current [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/).                                                        |
 | [browser.isConnected](/javascript-api/k6-experimental/browser/isconnected) <BWIPT id="453"/>  | Indicates whether the [CDP](https://chromedevtools.github.io/devtools-protocol/) connection to the browser process is active or not.                  |
 | [browser.newContext([options])](/javascript-api/k6-experimental/browser/newcontext/) <BWIPT id="455"/> | Creates and returns a new [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/).                                                             |
 | [browser.newPage([options])](/javascript-api/k6-experimental/browser/newpage)  <BWIPT id="455"/>       | Creates a new [Page](/javascript-api/k6-experimental/browser/page/) in a new [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/) and returns the page. |

src/data/markdown/docs/02 javascript api/07 k6-experimental/01 browser/contexts.md

@@ -1,15 +1,21 @@
 ---
 title: 'contexts()'
-excerpt: 'Browser module: contexts method'
+excerpt: 'Browser module: context method'
 ---
 
-Access all open [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/)s.
+Returns the current [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/).
+
+<Blockquote mod="note" title="">
+
+A 1-to-1 mapping between [Browser](/javascript-api/k6-experimental/browser) and `BrowserContext` means you cannot run `BrowserContexts` concurrently. If you wish to create a new `BrowserContext` while one already exists, you will need to [close](/javascript-api/k6-experimental/browser/browsercontext/close) the current one, and create a new one with either [newContext](/javascript-api/k6-experimental/browser/newcontext/) or [newPage](/javascript-api/k6-experimental/browser/newpage). All resources associated to the closed `BrowserContext` will also be closed and cleaned up (such as [Page](/javascript-api/k6-experimental/browser/page/)s).
+
+</Blockquote>
 
 ### Returns
 
-| Type  | Description                                                                    |
-| ----- | ------------------------------------------------------------------------------ |
-| Array | Array of [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/) objects |
+| Type           | Description                                                                                                                              |
+| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
+| object \| null | The current [BrowserContext](/javascript-api/k6-experimental/browser/browsercontext/) if one has been created, otherwise `null`. |
 
 
 ### Example
@@ -31,11 +37,13 @@ export const options = {
 }
 
 export default function () {
-  console.log(browser.contexts().length); // 0
+  console.log(browser.context()); // null
 
-  const context = browser.newContext();
-  console.log(browser.contexts().length); // 1
+  const page = browser.newPage();
+  const context = browser.context();
+  console.log(context); // {"base_event_emitter":{}}
 
+  page.close();
   context.close();
 }
 ```