Task #1892: using consistently the official name for the SIR operator

.gitattributes

...agger/include/AOFlagger/strategy/algorithms/siroperator.h

...de/AOFlagger/test/experiments/rankoperatorrocexperiment.h

...agger/test/experiments/scaleinvariantdilationexperiment.h

.../AOFlagger/test/strategy/algorithms/algorithmstestgroup.h

...lude/AOFlagger/test/strategy/algorithms/siroperatortest.h

.../AOFlagger/src/strategy/actions/statisticalflagaction.cpp