Paul Jolly observes that returning interface{} is not helpful.
Now CodeAction() returns []CodeAction.
The type in typescript is (Command | CodeAction)[] | null
but the choice is up to gopls, which returns []CodeAction.
Fixesgolang/go#35688, golang/go#35679
Change-Id: I91c22bb0752431954ae2f993cb7b44726cf60e5c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/207898
Reviewed-by: Rebecca Stambler <rstambler@golang.org>