Clarify: all rules in a group are concomitant (#8248)
Clarify: all rules in a group are concomitant (#8248)

Improve the documentation to clarify the differences beetween rules in a
group and outside a group.

Signed-off-by: Thibault Jamet <98f8ba98fa8f98b2aadf989d1b543be75eac9f81@users.noreply.github.com>
keegancsmith/prometheus,alileza/prometheus,keegancsmith/prometheus,alileza/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,keegancsmith/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,alileza/prometheus,keegancsmith/prometheus,prometheus/prometheus,prometheus/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus