ENH: Add valgrind suppression file for Ubuntu 20.04
ENH: Add valgrind suppression file for Ubuntu 20.04

The file is initially a copy of the Ubuntu 18.04 suppression file,
which contains suppressions for existing false positive defects on the
dashboard.

hjmjohnson/ITK,Kitware/ITK,Kitware/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,richardbeare/ITK,Kitware/ITK,hjmjohnson/ITK,richardbeare/ITK,BRAINSia/ITK,BRAINSia/ITK,richardbeare/ITK,Kitware/ITK,richardbeare/ITK,BRAINSia/ITK,hjmjohnson/ITK,hjmjohnson/ITK,thewtex/ITK,hjmjohnson/ITK,BRAINSia/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,Kitware/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,thewtex/ITK,thewtex/ITK,BRAINSia/ITK,Kitware/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,richardbeare/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK