update xcu.yaml with new fpa focus position

The ImageQuality of IIS has been degraded (cf. INSTRM-2768). 

From fpaThroughFocus and/or detectorThroughFocus sequence, new FPA position was measured.

xcu_b1 motors moveCcd a=166.71 b=114.53 c=84.34 microns abs

xcu_b2 motors moveCcd a=241.42 b=259.41 c=247.72 microns abs

xcu_b3 motors moveCcd a=197.23 b=187.09 c=197.35 microns abs

xcu_b4 motors moveCcd a=131.69 b=94.08 c=149.89 microns abs

xcu_r1 motors moveCcd a=177.26 b=134.17 c=111.52 microns abs

xcu_r2 motors moveCcd a=174.77 b=203.92 c=181.34 microns abs

xcu_r3 motors moveCcd a=213.20 b=204.29 c=203.66 microns abs

xcu_r4 motors moveCcd a=117.05 b=69.89 c=112.59 microns abs

xcu_n2 motors move piston=10 microns

xcu_n3 motors move piston=10 microns'

Note that the cameras in the SM tend to show similar defocus within 10~20um.