chore: remove unnecessary transform-for-of when building babel-parser

[JLHwung]

Q	A
Tests Added + Pass?	Yes
License	MIT

This PR applies transform-for-of: assumeArray on standalone build, of which the size decrease is expected.

It removes this transform from babel-parser build config since it is supported in Node >= 6.

[nicolo-ribaudo]

I'd prefer that we also apply this transform when running tests outside of @babel/standalone, otherwise we risk introducing a for-of with a Map which isn't caught by the tests.

[nicolo-ribaudo]

Actually, this probably already breaks part of @babel/core and all the modules plugins.

[JLHwung]

That's an interesting usage of this plugin! I will try it later.

[nicolo-ribaudo]

Yup, it doesn't work:

https://babeljs.io/repl/build/13296#?browsers=Chrome%2023&build=&builtIns=false&spec=false&loose=false&code_lz=JYWwDg9gTgLgBAbzgDzgXzgMyhEcBEARvgNwBQZApspLHAG4CGUcjcAvCiUA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=true&presets=es2015&prettier=false&targets=&version=7.7.4%2Bpr.10823&externalPlugins=

[JLHwung]

@nicolo-ribaudo I revised this PR to be minimal: It only removes unnecessary transform-for-of for babel-parser.

[nicolo-ribaudo]

How much bigger it the new bundle size? (Since it will now use the "default" transform for for-of)

[JLHwung]

@nicolo-ribaudo The unminified babel-preset-env.js increases from 3.0MB to 3.1MB. I will work on a fix later.