Add Indirect Geometry Diffraction as technique for VESUVIO. Refs #6733

This means it only shows up in the diffraction GUI & not the convert
to energy one.

Code/Mantid/instrument/Facilities.xml

@@ -134,6 +134,7 @@
 
   <instrument name="VESUVIO" shortname="EVS">
     <technique>Neutron Compton Scattering</technique>
+    <technique>TOF Indirect Geometry Diffraction</technique>
     <livedata address="NDXVESUVIO:6789" />
   </instrument>