chore(poetry): fix copy-paste error

plugins/poetry/poetry.plugin.zsh

@@ -8,7 +8,7 @@ fi
 if [[ ! -f "$ZSH_CACHE_DIR/completions/_poetry" ]]; then
   typeset -g -A _comps
   autoload -Uz _poetry
-  _comps[gh]=_poetry
+  _comps[poetry]=_poetry
 fi
 
 poetry completions zsh >| "$ZSH_CACHE_DIR/completions/_poetry" &|