Update text.md

Remove inaccurate description.

Not sure if this was a limitation on a previous version. but calling this without a callback function just worked in the tutorial page

site/content/tutorial/06-bindings/14-component-this/text.md

@@ -15,9 +15,7 @@ Just as you can bind to DOM elements, you can bind to component instances themse
 Now we can programmatically interact with this component using `field`.
 
 ```html
-<button on:click="{() => field.focus()}">
+<button on:click="{field.focus}">
 	Focus field
 </button>
 ```
-
-> Note that we can't do `{field.focus}` since field is undefined when the button is first rendered and throws an error.