This rule aims to eliminate unnecessary and potentially confusing lone
`<template>` tags in Vue components.

In Vue.js 2.x, `<template>` elements that have no specific directives
have no effect.

In Vue.js 3.x, `<template>` elements that have no specific directives
render `<template>` DOM elements as is, but in most cases this may not
be what is intended.

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/297218.