Fix UT stripID mask
The UT stripID information only requires 9 bit. Changes the UT stripID mask to only read the 9 stripID bits. Corresponding MR for HLT2: LHCb!4528 (merged)
The UT stripID information only requires 9 bit. Changes the UT stripID mask to only read the 9 stripID bits. Corresponding MR for HLT2: LHCb!4528 (merged)