update xcu.yaml of pfs_instdata with new r-camera focus position

After VPHG MR flipping r cameras were cooled down and their focus position were re-measured. Update accordingly.

• r1: xcu_r1 motors moveCcd a=176.79 b=178.82 c=142.24 microns abs
• r2: xcu_r2 motors moveCcd a=162.18 b=190.04 c=152.87 microns abs
• r3: xcu_r3 motors moveCcd a=194.08 b=188.06 c=181.47 microns abs
• r4: xcu_r4 motors moveCcd a=92.71 b=64.41 c=60.89 microns abs