Update a11y-semantics.md (#991)

Fix typo.

Author: mstnorris

src/guide/a11y-semantics.md

@@ -76,7 +76,7 @@ Feel free to inspect this element in Chrome DevTools to see how the accessible n
 
 #### aria-labelledby
 
-Using [`aria-labelledby`](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_aria-labelledby_attribute) is similar to `aria-label` expect it is used if the label text is visible on screen. It is paired to other elements by their `id` and you can link multiple `id`s:
+Using [`aria-labelledby`](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_aria-labelledby_attribute) is similar to `aria-label` except it is used if the label text is visible on screen. It is paired to other elements by their `id` and you can link multiple `id`s:
 
 ```html
 <form
@@ -106,7 +106,7 @@ Using [`aria-labelledby`](https://developer.mozilla.org/en-US/docs/Web/Accessibi
 
 #### aria-describedby
 
-[aria-describedby](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_aria-describedby_attribute) is used the same way as `aria-labelledby` expect provides a description with additional information that the user might need. This can be used to describe the criteria for any input:
+[aria-describedby](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_aria-describedby_attribute) is used the same way as `aria-labelledby` except provides a description with additional information that the user might need. This can be used to describe the criteria for any input:
 
 ```html
 <form