docs: Explicitly mention what is thrown (testing-library#720)

Author: aleks-rope

docs/dom-testing-library/api-queries.mdx

@@ -26,7 +26,7 @@ an error if no elements match.
 
 `queryBy*` queries return the first matching node for a query, and return `null`
 if no elements match. This is useful for asserting an element that is not
-present. This throws if more than one match is found (use `queryAllBy` instead).
+present. This throws an error if more than one match is found (use `queryAllBy` instead).
 
 ### queryAllBy