build(babel): Remove `@babel/polyfill` (#15564)

No longer needed due to https://github.com/getsentry/sentry/pull/14359

See the [release notes for babel@7.4.0](https://babeljs.io/blog/2019/03/19/7.4.0) for more information

package.json

@@ -13,7 +13,6 @@
     "@babel/plugin-proposal-object-rest-spread": "~7.6.2",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
     "@babel/plugin-transform-runtime": "~7.6.2",
-    "@babel/polyfill": "~7.7.0",
     "@babel/preset-env": "~7.7.1",
     "@babel/preset-react": "^7.7.0",
     "@babel/preset-typescript": "^7.7.2",

yarn.lock

@@ -1323,14 +1323,6 @@
     "@babel/helper-regex" "^7.0.0"
     regexpu-core "^4.1.3"
 
-"@babel/polyfill@~7.7.0":
-  version "7.7.0"
-  resolved "https://registry.yarnpkg.com/@babel/polyfill/-/polyfill-7.7.0.tgz#e1066e251e17606ec7908b05617f9b7f8180d8f3"
-  integrity sha512-/TS23MVvo34dFmf8mwCisCbWGrfhbiWZSwBo6HkADTBhUa2Q/jWltyY/tpofz/b6/RIhqaqQcquptCirqIhOaQ==
-  dependencies:
-    core-js "^2.6.5"
-    regenerator-runtime "^0.13.2"
-
 "@babel/preset-env@7.1.0":
   version "7.1.0"
   resolved "https://registry.yarnpkg.com/@babel/preset-env/-/preset-env-7.1.0.tgz#e67ea5b0441cfeab1d6f41e9b5c79798800e8d11"
@@ -4943,11 +4935,6 @@ core-js@^2.5.7:
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.1.tgz#87416ae817de957a3f249b3b5ca475d4aaed6042"
   integrity sha512-L72mmmEayPJBejKIWe2pYtGis5r0tQ5NaJekdhyXgeMQTpJoBsH0NL4ElY2LfSoV15xeQWKQ+XTTOZdyero5Xg==
 
-core-js@^2.6.5:
-  version "2.6.9"
-  resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.9.tgz#6b4b214620c834152e179323727fc19741b084f2"
-  integrity sha512-HOpZf6eXmnl7la+cUdMnLvUxKNqLUzJvgIziQ0DiF3JwSImNphIqdGqzj6hIKyX04MmV0poclQ7+wjWvxQyR2A==
-
 core-js@^3.2.1:
   version "3.2.1"
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.2.1.tgz#cd41f38534da6cc59f7db050fe67307de9868b09"