fix(babel-preset-gatsby-package): remove explicit @babel/plugin-proposal-class-properties and let @babel/preset-env add it (#24640)

* fix error from babel about `loose: true`

* update snapshots for tests

* remove @babel/plugin-proposal-class-properties

* update jest snapshots

* remove class-properties from dependencies

Co-authored-by: gatsbybot <mathews.kyle+gatsbybot@gmail.com>

Author: Js-Brecht

packages/babel-preset-gatsby-package/__tests__/__snapshots__/index.js.snap

@@ -54,7 +54,6 @@ Array [
 
 exports[`babel-preset-gatsby-package in browser mode specifies the proper plugins 1`] = `
 Array [
-  "@babel/plugin-proposal-class-properties",
   "@babel/plugin-proposal-nullish-coalescing-operator",
   "@babel/plugin-proposal-optional-chaining",
   "@babel/plugin-transform-runtime",
@@ -111,7 +110,6 @@ Array [
 
 exports[`babel-preset-gatsby-package in node mode specifies the proper plugins 1`] = `
 Array [
-  "@babel/plugin-proposal-class-properties",
   "@babel/plugin-proposal-nullish-coalescing-operator",
   "@babel/plugin-proposal-optional-chaining",
   "@babel/plugin-transform-runtime",

packages/babel-preset-gatsby-package/index.js

@@ -4,7 +4,7 @@ function preset(context, options = {}) {
   const { browser = false, debug = false, nodeVersion = `10.13.0` } = options
   const { NODE_ENV, BABEL_ENV } = process.env
 
-  const IS_TEST  = (BABEL_ENV || NODE_ENV) === `test`
+  const IS_TEST = (BABEL_ENV || NODE_ENV) === `test`
 
   const browserConfig = {
     useBuiltIns: false,
@@ -39,12 +39,11 @@ function preset(context, options = {}) {
       r(`@babel/preset-flow`),
     ],
     plugins: [
-      r(`@babel/plugin-proposal-class-properties`),
       r(`@babel/plugin-proposal-nullish-coalescing-operator`),
       r(`@babel/plugin-proposal-optional-chaining`),
       r(`@babel/plugin-transform-runtime`),
       r(`@babel/plugin-syntax-dynamic-import`),
-      IS_TEST && r(`babel-plugin-dynamic-import-node`)
+      IS_TEST && r(`babel-plugin-dynamic-import-node`),
     ].filter(Boolean),
     overrides: [
       {

packages/babel-preset-gatsby-package/package.json

@@ -9,7 +9,6 @@
   },
   "homepage": "https://github.com/gatsbyjs/gatsby/tree/master/packages/babel-preset-gatsby-package#readme",
   "dependencies": {
-    "@babel/plugin-proposal-class-properties": "^7.10.1",
     "@babel/plugin-proposal-nullish-coalescing-operator": "^7.10.1",
     "@babel/plugin-proposal-optional-chaining": "^7.10.1",
     "@babel/plugin-syntax-dynamic-import": "^7.8.3",