Improved typography on 'a more detailed example' (#22497)

On the 'a more detailed example' JS code, the showError() function display messages all but the last one referred 'e-mail' as e-mail. 
To standardize the error messages, I suggest changing the 'else if (email.validity.tooShort)' display error message "email" to 'e-mail'.
Just a small improvement.

files/en-us/learn/forms/form_validation/index.md

@@ -629,7 +629,7 @@ function showError() {
   } else if (email.validity.tooShort) {
     // If the data is too short,
     // display the following error message.
-    emailError.textContent = `Email should be at least ${email.minLength} characters; you entered ${email.value.length}.`;
+    emailError.textContent = `E-mail should be at least ${email.minLength} characters; you entered ${email.value.length}.`;
   }
 
   // Set the styling appropriately