Delete unneeded lexical classes in Prism grammars
Delete unneeded lexical classes in Prism grammars

Summary:
The Prism grammars include such token classes `punctuation` as `number`,
but my highlighting scheme doesn’t render those any differently from
normal text. In fact, I basically distinguish only three lexical
classes: normal text, keywords (bold), and strings/comments (light).
Everything else can is superfluous.

These superfluous strings were being rendered to long strings, so a
simple `.` became `<span style="punctuation">.</span>`. Removing them
reduces the bundle sizes significantly:

          Savings
     (bytes)    (rel.)  Article slug
     -----------------  -----------
       14136    0.3267  abusing-flow-comment-syntax-for-great-good
         606    0.0597  a-cute-autoincrementing-id-table-in-one-line-of-python
       24893    0.3030  dubious-dynamic-delegation-in-python
       16457    0.3690  encodings-and-assumptions
        3398    0.1709  hidden-edges-in-the-python-object-graph
           0    0.0000  managing-dependent-pull-requests

(The `managing-dependent-pull-requests` article uses only grammars that
I wrote, so the changes don’t affect it.)

(Note: these numbers are pre-gzip. The post-gzip deltas are of course
smaller, but still worth doing.)

Test Plan:
No visible changes, as far as I can tell.

wchargin/wchargin.github.io,wchargin/wchargin.github.io