Python: Remove `RegExpTerm` from PrintAST
Python: Remove `RegExpTerm` from PrintAST

Since this caused bad performance (as we had to evaluate points-to).

Fixes https://github.com/github/codeql/issues/6964

This approach was motivated by the comment on the issue from @tausbn:

> We discussed this internally in the CodeQL Python team, and have
> agreed that the best approach for now is to disable the printing of
> regex ASTs.

I tried to keep our RegExpTerm logic, but doing the fix below did not
work, and still evaluated RegExpTerm :| I guess we will just have to
revert this PR if we want it back

```diff
   TRegExpTermNode(RegExpTerm term) {
+    none() and
     exists(StrConst str | term.getRootTerm() = getParsedRegExp(str) and shouldPrint(str, _))
   }
```

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