Fixed threshold rule to match description

[kjakan]

Describe changes:

• Fixed threshold.conf rule examples to match description, based on documentation (https://suricata.readthedocs.io/en/suricata-6.0.3/rules/thresholding.html)

[catenacyber]

The doc change seems appropriate indeed cf https://suricata.readthedocs.io/en/suricata-6.0.0/rules/thresholding.html#type-threshold

[victorjulien]

Merged in #8861, thanks!