Review trivia which can't be inferred from their node kind

Some tokens becomes trivia after parsing has done its work. For example, parentheses in both `f(x)` and `(x)` only appear in the green tree as trivia. For the function call, the presence of parentheses can be inferred from the tree `(call f x)` because there's only one type of function call syntax. That is, we can reconstruct the trivia which isn't whitespace or comments.

In contrast, this is not the case for `(x)`, until #222 is merged because the green tree didn't represent grouping parentheses (these ended up as trivia on the parent node instead).

In general, it seems that a nice invariant for the green tree to have would be that

> Every piece of syntax can be inferred from the `kind`, `flags`, and list of nontrivia children, other than whitespace and comments.

Presumably there's cases other than #222 to fix - would be good to review all cases of `bump` used together with `TRIVIA_FLAG`.