app/assets/stylesheets/actiontext.scss
//=-require trix/dist/trixの行を削除
// // Provides a drop-in pointer for the default Trix stylesheet that will format the toolbar and // the trix-editor content (whether displayed or under editing). Feel free to incorporate this // inclusion directly in any other asset bundle and remove this file. // - //=-require trix/dist/trix // // We need to override trix.css’s image gallery styles to accommodate the // <action-text-attachment> element we wrap around attachments. Otherwise, // images in galleries will be squished by the max-width: 33%; rule.
参考：【解決方法】couldn't find file 'trix/dist/trix' with type 'text/css" とは？ #Rails - Qiita
