Simplify patch version updates (less steps)

Created by: Bufallo

In the documentations for minor version update docs (e.g. 7.14-to-8.0.md) the rake tasks assets:clean, assets:precompile and cache:clear are already merged into a single rake call:

sudo -u git -H bundle exec rake assets:clean assets:precompile cache:clear RAILS_ENV=production

This pull request updates the patch version documentation and merges 3 steps into a single one for a simpler patch level update process.