better fix for r.relief in grass7

Author: Giovanni Manghi

python/plugins/processing/algs/grass7/description/r.relief.txt

@@ -6,5 +6,4 @@ ParameterNumber|altitude|Altitude of the sun in degrees above the horizon|0|90|3
 ParameterNumber|azimuth|Azimuth of the sun in degrees to the east of north|0|360|270.0
 ParameterNumber|zscale|Factor for exaggerating relief|None|None|1.0
 ParameterNumber|scale|Scale factor for converting horizontal units to elevation units|None|None|1.0
-ParameterSelection|units|Elevation units (overrides scale factor)|intl;survey
 OutputRaster|output|Output shaded relief layer