'Use' for babel-loader and removed unused deps.

config/webpack.config.common.js

@@ -36,7 +36,7 @@ const webpackConfig = function(isDev) {
         },
         {
           test: /\.js$/,
-          loader: "babel-loader",
+          use: [ "babel-loader" ],
           include: [helpers.root("src")]
         },
         {

package.json

@@ -44,11 +44,6 @@
   },
   "devDependencies": {
     "@babel/core": "~7.12",
-    "@babel/plugin-proposal-class-properties": "~7.3",
-    "@babel/plugin-proposal-decorators": "~7.3",
-    "@babel/plugin-proposal-json-strings": "~7.2",
-    "@babel/plugin-syntax-dynamic-import": "~7.2",
-    "@babel/plugin-syntax-import-meta": "~7.2",
     "@babel/preset-env": "~7.12",
     "babel-loader": "~8.0",
     "compression-webpack-plugin": "^3.1.0",