Clarify that no configuration is needed for generating and saving metrics to _internal

The user is looking to install or configure this as a plugin. Can we add some text that clarifies that this does not require any configuration?

Change the first sentence from:
“By default, InfluxDB generates internal metrics and saves to the _internal database. Use these metrics to monitor InfluxDB and InfluxDB Enterprise and to create alerts to notify you when problems arise.”

to this:

After you install InfluxDB, InfluxDB generates internal metrics and saves them to the _internal database by default—there is no configuration necessary.

New user feedback!
Page: https://docs.influxdata.com/platform/monitoring/influxdata-platform/tools/measurements-internal/
Feedback: It gives absolutely no info on how to install or configure this plug_in

Open the measurements-internal documentation page linked in the issue and locate its introductory sentence about internal metrics and the _internal database. Confirm the wording addresses the feedback about installation and configuration, then verify the rendered page clearly states that no configuration is necessary after installation.

Written by the indexing model from the issue text.