fix nand and nor latex symbols

[mmatera]

No description provided.

[mmatera]

Update: the problem is the following. In the title of a section associated with an operator, the character of the operator is put inside a ``\code{\lstinline 'char' }```. As \lstinline expect verbatim code, it fails to understand math mode expressions.
In this PR I just removed `\lstinline` in a way that LaTeX accepts LaTeX code.

[rocky]

@mmatera in #1399 I used your observation that the problem was that the text is inside "inline" text and I revised the doc string so that the operators are now outside. In fact there are many places as far as formatting goes that when you have an operator expression like:

$expr1$ \u22BD $expr2$ \u22BD ...

I am not seeing any benefit in using the quotes at all. The benefit is only when there is an name like Nand (and maybe including the bracket. As a convenience to minimize the use of the quote I think the quote was extended to the closing bracket.

In that PR I also moved forward in using unicode in more of the operators that have no ASCII equivalent.

I am (slowly) moving towards the idea of replacing the ASCII operators like == too, but really, better would be to hook in all of that with mathics-scanner and have some way for it to fallback to the ASCII operators when the front end doesn't support that.

Should this PR be closed?