COMP: Remove RemoteSensingRegion assignment operator

Summary

The default copy and move constructors and assignment operators are fine, there's no need to implement them manually.

Rationale

Spotted on Debian Testing with GCC 9.2.1:

In file included from /otb/Modules/Core/VectorDataBase/include/otbPolyLineParametricPathWithValue.h:34,
                 from /otb/Modules/Core/VectorDataBase/include/otbPolygon.h:24,
                 from /otb/Modules/Core/LabelMap/include/otbAttributesMapLabelObject.h:33,
                 from /otb/Modules/Core/LabelMap/test/otbLabelObjectMapVectorizer.cxx:24:
/otb/Modules/Core/ImageBase/include/otbRemoteSensingRegion.h:118:8: note: because 'otb::RemoteSensingRegion<double>' has user-provided 'void otb::RemoteSensingRegion<TType>::operator=(const Self&) [with TType = double; otb::RemoteSensingRegion<TType>::Self = otb::RemoteSensingRegion<double>]'
  118 |   void operator=(const Self& region)
      |        ^~~~~~~~

Copyright

The copyright owner is Laurențiu Nicola (CS ROMANIA) and has signed the ORFEO ToolBox Contributor License Agreement.

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