Update README.md

Author: tommygonzaleza

README.md

@@ -65,8 +65,7 @@ $ npm i jest@24.8.0 -g
 $ learnpack start
 ```
 
-Note: The exercises have automatic grading but its very rigid and string, my recomendation is to ignore the tests and use them only as a recomendation or you can get frustrated.
-
+Note: The exercises have automatic grading but its very rigid and strict, my recomendation is to ignore the tests and use them only as a recomendation or you can get frustrated.
 
 ## How are the exercises organized?