colors: fix https://trac.osgeo.org/grass/changeset/60889 as Kelvin is not referred to as a degree

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@60904 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/gis/colors.desc

@@ -19,7 +19,7 @@ grey.eq: histogram-equalized grey scale
 grey.log: histogram logarithmic transformed grey scale
 gyr: green through yellow to red
 haxby: relative colors for bathymetry or topography
-kelvin: blue to red for degree Kelvin temperature
+kelvin: blue to red for temperature in Kelvin scale
 ndvi: Normalized Difference Vegetation Index colors
 ndwi: Normalized Difference Water Index colors
 population: color table covering human population classification breaks