Simplify instructions to change dashboards
Simplify instructions to change dashboards

This removes parts of the manual that aren't directly relevant to
the process of changing a dashboard. It's actually OK to change a
dashboard temporarily; the screenshot of part of the Puppet codebase
also appeared to be unrelated to the text above it.

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs