build(babel): Upgrade babel and babel plugins to 7.8.4 (#17016)

Upgrade babel and babel plugins to 7.8.4, remove babel-core, unneeded.

Author: billyvg

package.json

@@ -7,16 +7,16 @@
     "url": "git://github.com/getsentry/sentry.git"
   },
   "dependencies": {
-    "@babel/core": "~7.8.3",
-    "@babel/plugin-proposal-class-properties": "~7.7.0",
-    "@babel/plugin-proposal-decorators": "~7.7.0",
-    "@babel/plugin-proposal-object-rest-spread": "~7.6.2",
+    "@babel/core": "~7.8.4",
+    "@babel/plugin-proposal-class-properties": "~7.8.3",
+    "@babel/plugin-proposal-decorators": "~7.8.3",
+    "@babel/plugin-proposal-object-rest-spread": "~7.8.3",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
-    "@babel/plugin-transform-runtime": "~7.6.2",
-    "@babel/preset-env": "~7.8.3",
+    "@babel/plugin-transform-runtime": "~7.8.3",
+    "@babel/preset-env": "~7.8.4",
     "@babel/preset-react": "^7.7.0",
     "@babel/preset-typescript": "^7.7.2",
-    "@babel/runtime": "~7.7.2",
+    "@babel/runtime": "~7.8.4",
     "@emotion/babel-preset-css-prop": "^10.0.27",
     "@emotion/core": "^10.0.27",
     "@emotion/styled": "^10.0.27",
@@ -47,7 +47,6 @@
     "@types/reflexbox": "^4.0.0",
     "@types/reflux": "0.4.1",
     "algoliasearch": "^3.32.0",
-    "babel-core": "^7.0.0-bridge.0",
     "babel-loader": "^8.0.0",
     "babel-plugin-add-react-displayname": "^0.0.5",
     "babel-plugin-transform-react-remove-prop-types": "^0.4.24",