[Security] Bump sprockets from 3.7.1 to 3.7.2
[Security] Bump sprockets from 3.7.1 to 3.7.2

Bumps [sprockets](http://getsprockets.org/) from 3.7.1 to 3.7.2. **This update includes security fixes.**

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
alphagov/release,alphagov/release,alphagov/release