For some reason, running `npm update vue` didn't have much of an effect.
I suspect that has to do with the @vue/test-utils dependency on
@vue/server-renderer, which requires an exactly matching version of vue.
I temporarily uninstalled @vue/test-utils, and afterwards,
`npm update vue` updated vue successfully. I then reinstalled
@vue/test-utils and confirmed that it was using the latest versions of
@vue/server-renderer and vue.

I ran the following commands:

npm uninstall @vue/test-utils
npm update vue
npm install -D @vue/test-utils
npm ls vue

I can see that @vue/compiler-sfc was updated as well.