Assessors should get a clear message when 'replacing' a file

[Rebecca-mcknight1991]

As an Assessor/Admin I am frustrated that when I replace a document on the Assessments I do not get a clear confirmation message.

When you replace the file a green banner should appear confirming submission. It might even say 'Replacement successful' to be 100% clear.

Feedback from Alza.

[warrensearle]

For now when a user chooses to replace an uploaded file let's change the message to say "Your file has been replaced"

[warrensearle]

Checked with @Rebecca-mcknight1991 and this is working as expected, so moving to Reviewed.
A separate bug was spotted during testing which is captured in #65 so is outside scope of this ticket.