In docs, move commas out of code

The commas separating these three keywords are not code themselves – not what the user would write – so they should be outside of the `<tt>` tags.

Edits the table in the section [Operators and Aliases](http://coffeescript.org/#operators).
In docs, move commas, part 2

I had missed that the next line had comma-separated operators, too.
Merge pull request #3337 from roryokane/fix-operator-docs-commas

In docs, move commas out of code