OTB 6.6-rc1 fails to build on Debian unstable (fatal error: shark/Models/Classifier.h: No such file or directory)

Description

OTB 6.6-rc1 fails to build on Debian unstable because it cannot find a shark header:

make -f Modules/Applications/AppClassification/app/CMakeFiles/otbapp_MultiImageSamplingRate.dir/build.make Modules/Applications/AppClassification/app/CMakeFiles/otbapp_MultiImageSamplingRate.dir/depend
In file included from /build/otb-6.6.0~rc1+dfsg/Modules/Learning/Supervised/include/otbSharkRandomForestsMachineLearningModelFactory.txx:28:0,
                 from /build/otb-6.6.0~rc1+dfsg/Modules/Learning/Supervised/include/otbSharkRandomForestsMachineLearningModelFactory.h:74,
                 from /build/otb-6.6.0~rc1+dfsg/Modules/Learning/Supervised/include/otbMachineLearningModelFactory.txx:45,
                 from /build/otb-6.6.0~rc1+dfsg/Modules/Learning/Supervised/include/otbMachineLearningModelFactory.h:81,
                 from /build/otb-6.6.0~rc1+dfsg/Modules/Applications/AppClassification/app/otbVectorClassifier.cxx:33:
/build/otb-6.6.0~rc1+dfsg/Modules/Learning/Supervised/include/otbSharkRandomForestsMachineLearningModel.h:39:10: fatal error: shark/Models/Classifier.h: No such file or directory
 #include <shark/Models/Classifier.h>
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

This header is not included in libshark-dev (3.1.4+ds1-1)

Steps to reproduce

Build OTB 6.6-rc1 with -DOTB_USE_SHARK:BOOL=ON on Debian unstable.

Configuration information

Debian unstable, OTB 6.6-rc1.