You must set `enable` to `0`. It enable `hook/markdown_gfm` in all hook cases.

And you need to change `plugin/quickrun-markdown-gfm.vim` to the following

```vim
let g:quickrun_config['markdown/gfm'] = {
\   'exec': 'call quickrun_markdown_gfm#render()'
\ , 'runner': 'vimscript'
\ , 'hook/markdown_gfm/enable': 1
\ }
```