Fix for "Unknown command: hostname" error

[2meito]

When trying out the theme, every command would display the following error:

fish: Unknown command: hostname
~/.config/fish/functions/fish_prompt.fish (line 1): 
hostname|cut -d . -f 1
^~~~~~~^
in command substitution
	called on line 11 of file ~/.config/fish/functions/fish_prompt.fish
in function '__user_host'
	called on line 54 of file ~/.config/fish/functions/fish_prompt.fish
in function 'fish_prompt'
in command substitution
~/.config/fish/functions/fish_prompt.fish (line 11): Unknown command
  echo -n $USER@(hostname|cut -d . -f 1) (set color normal)
                ^~~~~~~~~~~~~~~~~~~~~~~^
in function '__user_host'
	called on line 54 of file ~/.config/fish/functions/fish_prompt.fish
in function 'fish_prompt'
in command substitution

Referencing other oh-my-fish themes, it seems the preferred way of getting the hostname is with uname -n.