BUG: Revert changing call to `Initialize()` with `clear()`
BUG: Revert changing call to `Initialize()` with `clear()`

This is a follow up of commit [1].
The method `clear()` has been used successfully in itkBoundingBox
for more than 10 years. There is no reason to replace it with a
call of the method `Initialize()`.

[1] 3a7ce4b6d8c76e30e6b89ddc850d5745b18a45d3

thewtex/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,malaterre/ITK,richardbeare/ITK,hjmjohnson/ITK,malaterre/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,richardbeare/ITK,vfonov/ITK,thewtex/ITK,hjmjohnson/ITK,LucasGandel/ITK,malaterre/ITK,malaterre/ITK,vfonov/ITK,BRAINSia/ITK,vfonov/ITK,vfonov/ITK,vfonov/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,thewtex/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,Kitware/ITK,Kitware/ITK,LucasGandel/ITK,LucasGandel/ITK,vfonov/ITK,BRAINSia/ITK,vfonov/ITK,Kitware/ITK,Kitware/ITK,LucasGandel/ITK,Kitware/ITK,hjmjohnson/ITK,BRAINSia/ITK,thewtex/ITK,BRAINSia/ITK,hjmjohnson/ITK,vfonov/ITK,richardbeare/ITK,vfonov/ITK,malaterre/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,Kitware/ITK,hjmjohnson/ITK,richardbeare/ITK,BRAINSia/ITK,LucasGandel/ITK,BRAINSia/ITK,richardbeare/ITK,malaterre/ITK,malaterre/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,thewtex/ITK,LucasGandel/ITK,malaterre/ITK,richardbeare/ITK