ATLASRECTS-5513: Increasing CaloClusterEt from 3 to 4.5GeV for TRT_TrackSegmentsFinder.h

We want to try increasing the Et cut used for TRT TrackSegment finding to make it behave a bit better in higher pile-up environments. A lot of TRT segments are now made that are not used so it would be good to limit this a bit. Private test shows minimal impact on Si-tracks.

Tagging egamma so that they can keep an eye on the ART @turra @dboerner

FYI: @goblirsc @christos @sroe

This will change the output so the digest will need to be updated I suspect