Update SCC tuning
Updating SCC tuning instructions as per https://it.overleaf.com/project/645509df6974e43cab141f26 by @braciti
The copy in Overleaf should then be deprecated/be make read-only and ideally link to https://ph2acf.docs.cern.ch/innerTracker/SCCTuning/
Edited by Clemens Lange