Readme check examples are invalid

[asachs01]

If readers choose to copy the examples from the readme, they'll be presented with an error:
check interval must be greater than 0 or a valid cron schedule must be provided

The minimum required attributes are found in the docs here and they should be reflected in the check examples: https://docs.sensu.io/sensu-go/latest/observability-pipeline/observe-schedule/checks/#check-example-minimum-recommended-attributes