style(afowler): simplify code and remove unnecessary variables

themes/afowler.zsh-theme

-if [ $UID -eq 0 ]; then CARETCOLOR="red"; else CARETCOLOR="blue"; fi
-
-local return_code="%(?..%{$fg[red]%}%? ↵%{$reset_color%})"
-
-PROMPT='%m %{${fg_bold[blue]}%}:: %{$reset_color%}%{${fg[green]}%}%3~ $(git_prompt_info)%{${fg_bold[$CARETCOLOR]}%}»%{${reset_color}%} '
-
-RPS1="${return_code}"
+PROMPT='%m %B%F{blue}:: %b%F{green}%3~ $(git_prompt_info)%B%(!.%F{red}.%F{blue})»%f%b '
+RPS1='%(?..%F{red}%? ↵%f)'
 
 ZSH_THEME_GIT_PROMPT_PREFIX="%{$fg[yellow]%}‹"
 ZSH_THEME_GIT_PROMPT_SUFFIX="› %{$reset_color%}"