Fix incorrect grammar (#5626)

* Fix incorrect grammar

* Update docs/rationale.md

Co-Authored-By: gnapse <gnapse@gmail.com>

docs/rationale.md

@@ -222,7 +222,7 @@ describe("NodeRegistry", () => {
 });
 ```
 
-Prettier special cases common test framework functions such as `describe`, `it` and `test`.
+Prettier has special cases for common testing framework functions such as `describe`, `it` and `test`.
 
 ### JSX