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.

Former-commit-id: b520f6972bf3158bfde470c7b9eb609e894d0494 [formerly 227aae73de310b68ac958be116c8533da36510c2]
Former-commit-id: b46b86c779311d9d2357bb4ace17a83e757fb21a
Former-commit-id: 2cc88e9037b5053d060296f5b8475506c7cf6945
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox