COMP: Remove duplicate MetricType definition

Change-Id: I1f2d21517cac9662ab68e1109d6c5ebec1a11580
Update ImageRegistrationMethod4.py for v4 revision

Change-Id: I7417ea85e0c48e300f911c7b84eb998683aefa2a
Merge topic 'SIMPLEITK-521_AddImageRegistrationMethodv4' into next

5d9a86de Update ImageRegistrationMethod4.py for v4 revision
6f455614 COMP: Remove duplicate MetricType definition