[Bug] Title of Enter the number of students with missing qualification needs changing

Overview
When navigating through the Missing qualification journey where a user selects Yes to the Does it affect the whole cohort question, a page is displayed where the user can enter the number of students with the missing qualification.
The title of that page is currently Enter the number of students with missing qualification which is different to the Figma images (but the Figma image was also wrong).
Praveen and Rob have discussed and updated the title accordingly to now be How many students are missing this qualification?

Steps to reproduce

1. Navigate to DEV/QA and sign-in.
2. Proceed through the pages: Check your student data > Report an issue with an exam result > Missing qualification and select Yes on the Does the missing qualification affect the whole cohort? page.
3. Note that the title of the following page where you can enter the number of students is entitled Enter the number of students with missing qualification.

Expected result
The title of that page should be How many students are missing this qualification?

Screenshots