Grief... to slow you down, it was on the 10.3.1 help topic reference
Georeferencing a raster to a vector—Help | ArcGIS for Desktop
I am just going to check to see if that functionality has been ported over to Pro as of yet. I will update this link when I am done, BUT, you can still georeferenced in 10.3.1 because you have it AND Pro isn't a replacement for 10.3.1 ... as of yet
UPDATE
George has the answer in this thread Re: Does ArcPro contain a georeferencing tool?
Who referenced Gabriel who linked... you get it
So basically Register Raster—Data Management toolbox | ArcGIS for Desktop
provides links to how to register rasters, warp and warp from file
So, you have to use ArcMap 10.3.1 if you want to use the georeferencing tool