typo in shell_layout example

Author: jarlebring

README.md

@@ -121,8 +121,8 @@ gplot(g, layout=spectral_layout)
 ### shell layout
 ```julia
 nlist = Vector{Vector{Int}}(undef, 2) # two shells
-nlist[1] = [1:5] # first shell
-nlist[2] = [6:nv(g)] # second shell
+nlist[1] = 1:5 # first shell
+nlist[2] = 6:nv(g) # second shell
 locs_x, locs_y = shell_layout(g, nlist)
 gplot(g, locs_x, locs_y, nodelabel=nodelabel)
 ```