Extended allow strip range to fix Overlay collection merging for ITkStrip
As discussed in ATLITKSW-192, the track efficiency for ITk Overlay samples was very low in the barrel region, due to an issue in the ITkStrips. This was eventually tracked down to the fact that strips beyond 768 (number of strips per module for SCT) were being ignored, while in the ITkStrip there are modules with up to 1536 strips (this number varies across the detector).
Since this number is just used to define a std::bitset of potential strips with hits, it should be safe to expand this to the maximum possible number, as any strip without a hit will anyway be ignored. Hopefully the CI tests will confirm this.