C:\...YourInstallFolder...\Resources\ArcPy\arcpy\sa\Raster.py
it is there.
Did you do a clean install? An install from the downloaded *.exe (or *.msi)? Or did you update through Pro?
through python
import arcpy.sa.Raster as R
dir(R)
['RAT', ... snip
'addDimension', 'appendSlices', 'bandCount', 'bandNames', 'bands', 'blockSize', 'catalogPath', 'compressionType', 'exportImage', 'extent',
...snip
'setVariableAttributes', 'slices', 'spatialReference', 'standardDeviation',
'uncompressedSize', 'variableNames', 'variables', 'width', 'write']
... sort of retired...