Incease max allowed upload size
Incease max allowed upload size

The default max upload size is small (<5MB) so we can't properly test
upload size validation locally as nginx errors before our apps.

Increasing the size here allows for a more reasitic dev environment.

alphagov/digitalmarketplace-functional-tests,alphagov/digitalmarketplace-functional-tests,alphagov/digitalmarketplace-functional-tests