Add back EM12 as monitored CTP item for lumi group

Daniele Zanzi requested to merge dzanzi/athena:ATR-EM12_dzanzi into master

in !49804 (merged), all CTP monitored items have been cleaned up in discussion with the L1CT experts as these would need to be added later on based on available CTP resources. However, in doing so I removed also EM12 that is needed by the lumi group. This MR brings this back

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