Bug Report

• I would like to work on a fix!

Current behavior
Babel removes the first-line comment unexpectedly.

• REPL, Codesandbox, or GitHub Repo helps!

Input Code

// test
import React from 'react';

export default class A extends B {}

Expected behavior
Keep the first-line comment(// test) in the output.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: babel.config.js

{
  "presets": ["@babel/preset-env"]
  "plugins": ["@babel/plugin-transform-runtime"]
}

- Babel version(s): v7.11.1
- Node/npm version: Node 10.13
- OS: MacOS 10.14.5
- Monorepo: no
- How you are using Babel: Playground

Additional context