Revert "Merge branch 'activateMDN' into 'master'" ATLASRECTS-5750

This reverts merge request !37772 (merged)

Activation of the MDN unfortunately had significant negative impacts on the CPU performance

where the switch slows the down the ambiguity processor! This amounts to about 40% of what the hole-search took and is not acceptable and can't be motivated by the modest physics performance improvements. Reverting this until this can be better understood.

pinging @gfacini @battagl @goblirsc @vcairo @sroe also @amete for information