[docs] make code samples in component lifecycle consistent (#1338)

Author: odanado

packages/lit-dev-content/site/docs/v2/components/lifecycle.md

@@ -58,7 +58,7 @@ In `connectedCallback()` you should setup tasks that should only occur when the
 ```js
 connectedCallback() {
   super.connectedCallback()
-  addEventListener('keydown', this._handleKeydown);
+  window.addEventListener('keydown', this._handleKeydown);
 }
 ```
 ### disconnectedCallback() {#disconnectedcallback}

packages/lit-dev-content/site/docs/v3/components/lifecycle.md

@@ -58,7 +58,7 @@ In `connectedCallback()` you should setup tasks that should only occur when the
 ```js
 connectedCallback() {
   super.connectedCallback()
-  addEventListener('keydown', this._handleKeydown);
+  window.addEventListener('keydown', this._handleKeydown);
 }
 ```
 ### disconnectedCallback() {#disconnectedcallback}