docs: update WebPreferences default values for Electron 12 (#29710)

Updates the values for `contextIsolation` and `worldSafeExecuteJavaScript` for Electron 12.

Co-authored-by: Erick Zhao <[email protected]>

docs/api/browser-window.md

@@ -339,7 +339,7 @@ It creates a new `BrowserWindow` with native properties as set by the `options`.
       more details.
     * `contextIsolation` Boolean (optional) - Whether to run Electron APIs and
       the specified `preload` script in a separate JavaScript context. Defaults
-      to `false`. The context that the `preload` script runs in will only have
+      to `true`. The context that the `preload` script runs in will only have
       access to its own dedicated `document` and `window` globals, as well as
       its own set of JavaScript builtins (`Array`, `Object`, `JSON`, etc.),
       which are all invisible to the loaded content. The Electron API will only
@@ -351,8 +351,7 @@ It creates a new `BrowserWindow` with native properties as set by the `options`.
       context in the dev tools by selecting the 'Electron Isolated Context'
       entry in the combo box at the top of the Console tab.
     * `worldSafeExecuteJavaScript` Boolean (optional) - If true, values returned from `webFrame.executeJavaScript` will be sanitized to ensure JS values
-      can't unsafely cross between worlds when using `contextIsolation`.  The default
-      is `false`. In Electron 12, the default will be changed to `true`. _Deprecated_
+      can't unsafely cross between worlds when using `contextIsolation`. Defaults to `true`. _Deprecated_
     * `nativeWindowOpen` Boolean (optional) - Whether to use native
       `window.open()`. Defaults to `false`. Child windows will always have node
       integration disabled unless `nodeIntegrationInSubFrames` is true. **Note:** This option is currently