Fix channel number in generation parameters

Tag: @ewelina @mnowak @tsulaia

In a previous patch we updated the run and MC channel numbers in event information and file metadata (!37564 (merged)). When using EVNT files with these corrections in simulations that do not have commit 447f6676. The reason being that the attributes for the generation parameters still live under the original MC channel number. This updates the channel number where the generation parameters may be found, if we are changing the run and MC channel numbers during EVNT-to-EVNT filtering.

Should these changes appear in places other than 21.6?

Should we also follow a similar procedure in derivation by adding another AODFix?