MDL-54802 mod_quiz: Move grade to pass error to require passing grade element
MDL-54802 mod_quiz: Move grade to pass error to require passing grade element

When using a passing grade of zero, with the required passing grade
option, an error was displayed on the "grade to pass" element.
This was confusing as the error message is referring to the
"Require passing grade" element. This patch moves the message to
the "Require passing grade" element.

Additionaly this patch fixes a small typo in a comment.

dilawar/moodle