DOC: utils: bcolors and shell_colours were duplicated. So I removed shell_colours.
DOC: utils: bcolors and shell_colours were duplicated. So I removed shell_colours.

3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox