fix: remove duplicate item in colorscheme

[fcying]

Description

When using lazy.nvim's lazy loading colorscheme, Telescope's colorscheme cannot see the lazily loaded colorscheme.
In this case, I used the colors parameter to add the colorscheme.

require("telescope.builtin").colorscheme({
    colors = {"rose-pine-dawn", "everforest", }
})

If I open the Telescope's colorscheme twice(first time select rose-pine-dawn), duplicate entries will appear.

• My code follows the style guidelines of this project (stylua)
• I have performed a self-review of my own code

[jamestrew]

thanks!