Removing label from a contour plot


I am trying to remove the following labels from a contour plot, but I cannot find the attribute for it.

This is the code to generate the plot:

using Plots
julia> c(x,y) = x^2 + y^2 -1
c (generic function with 1 method)

julia> contour(-1:0.01:1, -1:0.01:1, c, levels = [0])

Which returns the following output:

The axis I want to remove is the right y axis, and neither xticks, yticks or zticks seems to affect it.

Thats not an additional y-axis, it is the colorbar ( which only has one entry, in this example ).
To disable it use

contour(-1:0.01:1, -1:0.01:1, c, levels = [0], colorbar = false)