AUR is community driven by volunteers which are called maintainers. You can update the PKGBUILD yourself and it does indeed work (I did this manually all the time) but it may require a bit of text editing and whatnot. However, if you make an account on the AUR, you can flag the package out-of-date and post a link to the topic of the newest release and that'll help the package maintainer and the users.
I used to flag it every time a new build came out, but I stopped doing so after I switched from Arch Linux to Fedora as my main distro. I went ahead and flagged it and posted a link to the 30.0.87 topic, but I highly suggest someone actively using Arch Linux or Manjaro to do so in the future.