Fixed "Invalid face reference: quote" error.

[renatoathaydes]

Hi, I was unable to htmlize a buffer I wanted to.

Got the error "Invalid face reference: quote".

Debugging this code , I found out that the htmlize-face-size function was getting an erroneous value when calling (last tail) on the tail's cdr created with (cl-copy-list inherit).

I couldn't figure out why exactly, but it seems that inherit was not a "proper" list, it was a cons (listp returns t for cons anyway)... so it was getting a broken list with a quote element inside it.

Hence, I decided to just simplify the code because as far as I can see, the only purpose of this cond branch I changed was to set tail to the last element of inherit... As inherit was not even used after that, I think the copy was unnecessary...

I've tested the code after this change on several buffers and it worked every time, so I hope you accept the PR or at least find a better fix from the information here.

By the way, htmlfontify-buffer also fails with this error but it seems to use completely different code.

Thanks!