Update post.hbs

fix this:
<code>
~/blog/node_modules/express-hbs/node_modules/handlebars/dist/cjs/handlebars/compiler/parser.js:104
    throw new Error(str);
          ^
Error: Lexical error on line 21. Unrecognized text.
... </article>  {{!-- {{> comments}} --}
<code>