Delete deprecated pure theme

themes/pure.zsh-theme

-print -P '%F{yellow}'Oh My Zsh pure theme:
-cat <<-EOF
-
-	  The pure theme has been renamed as 'refined' as per the original author's
-	  request. Change your ZSH_THEME to 'refined' to avoid seeing this warning.
-
-EOF
-print -P '%f'
-
-source ${0:h:A}/refined.zsh-theme