Fix malformed ```ts section (SharePoint#896)

Author: JLRishe

docs/spfx/extensions/get-started/using-page-placeholder-with-extensions.md

@@ -45,13 +45,12 @@ In the following steps, you'll modify the Hello World Application Customizer to
 
 	  Also add the following import statements after the `strings` import at the top of the file:
 
+	```ts
+	import styles from './AppCustomizer.module.scss';
+	import { escape } from '@microsoft/sp-lodash-subset'; 
+	```
 
-	 ```ts
-	 import styles from './AppCustomizer.module.scss';
-	 import { escape } from '@microsoft/sp-lodash-subset'; 
-	 ```
-
-	  You use `escape` to escape Application Customizer properties. You'll create style definitions for the output in the following steps.  
+	You use `escape` to escape Application Customizer properties. You'll create style definitions for the output in the following steps.  
 
 3. Create a new file named **AppCustomizer.module.scss** under the **src\extensions\helloWorld** folder.