Disable git_icons in init.lua to fix whitespace errors in menu

[EmreDogann]

• The nvim_possession.list() menu throws errors about being unable to find the saved session file.
  • Caused by extra leading whitespace on the filename. This can be due to file_icons and git_icons being enabled in the list preview.

Example:

Error executing vim.schedule lua callback: .../nvim/lazy/nvim-possession/lua/nvim-possession/utils.lua:10: bad argument #1 to 'lines'
(/home/user/local/share/nvim/sessions/    nvim-config: No such file or directory)
stack traceback:
        [C]: in function 'lines'
        .../nvim/lazy/nvim-possession/lua/nvim-possession/utils.lua:10: in function 'session_files'
        ...share/nvim/lazy/nvim-possession/lua/nvim-possession/ui.lua:21: in function 'poputate_preview_buf'
        ...share/nvim/lazy/fzf-lua/lua/fzf-lua/previewer/builtin.lua:261: in function 'poputate_preview_buf'
        ...share/nvim/lazy/fzf-lua/lua/fzf-lua/previewer/builtin.lua:287: in function ''
        vim/_editor.lua: in function ''
        vim/_editor.lua: in function <vim/_editor.lua:0>
Press ENTER or type command to continue

Resolution:

• Disable git_icons for the list() menu.

Resolves #24