Fix zsh completion with multiple words
Fix zsh completion with multiple words

`${words[2,-2]}` must not be quoted, otherwise completion for multiple
words (e.g. `shell 3.4.1`) fails.

pyenv/pyenv,fly19890211/pyenv,syndbg/goenv,dnsd/pyenv,rowhit/pyenv,cehoffman/pyenv,habinmusic/pyenv,VShangxiao/pyenv,rowhit/pyenv,BanzaiMan/pyenv,pyenv/pyenv,takluyver/pyenv,chenfengyuan/pyenv,recruit-mtl/pyenv,sebhahn/pyenv,sebhahn/pyenv,cehoffman/pyenv,hlecuanda/pyenv,obimod/pyenv,xshwy/pyenv,lozybean/pyenv,UCASREN/pyenv,habinmusic/pyenv,yeonsh/pyenv,kevinburke/pyenv,UCASREN/pyenv,zmwangx/pyenv,recruit-mtl/pyenv,xshwy/pyenv,yyuu/pyenv,syndbg/goenv,yyuu/pyenv,BanzaiMan/pyenv,lepture/pyenv,chenfengyuan/pyenv,sebhahn/pyenv,dongguangming/pyenv,pyenv/pyenv,takluyver/pyenv,genome-vendor/pyenv,syndbg/goenv,VShangxiao/pyenv,dongguangming/pyenv,yeonsh/pyenv,lepture/pyenv,zmwangx/pyenv,obimod/pyenv,kevinburke/pyenv,syndbg/goenv,genome-vendor/pyenv,fly19890211/pyenv,dnsd/pyenv,hlecuanda/pyenv,lozybean/pyenv