Update shadow.mdx

Add missing quote

Author: MatthewSbar

docs/api/commands/shadow.mdx

@@ -96,7 +96,7 @@ When working with `cy.click()`, it sometimes won't click the right element in
 Chrome. It's happening because of
 [the ambiguity in spec](https://bugs.chromium.org/p/chromium/issues/detail?id=1188919&q=shadowRoot%20elementFromPoint&can=2).
 
-In this case, pass `'top` to `cy.click()` like below:
+In this case, pass `'top'` to `cy.click()` like below:
 
 ```js
 cy.get('#element')