[2.4.0] Checkmk Werk 16483 created: ntopng integration: remove ntopng version support for versions older than 6.0

[//]: # (werk v2) # ntopng integration: remove ntopng version support for versions older than 6.0 key | value ---------- | --- date | 2024-02-22T13:18:29+00:00 version | 2.4.0b1 class | fix edition | cee component | ntopng_integration level | 1 compatible | no Since Werk 16479 the ntopng integration was compatible with both ntopng versions newer than 6.0 and older than 6.0. With this change the ntopng integration no longer supports version older than 6.0.