Bump core-js from 2.5.7 to 2.6.4

Bumps [core-js](https://github.com/zloirock/core-js) from 2.5.7 to 2.6.4.
- [Release notes](https://github.com/zloirock/core-js/releases)
- [Changelog](https://github.com/zloirock/core-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/zloirock/core-js/compare/v2.5.7...v2.6.4)
Signed-off-by: dependabot[bot] <support@dependabot.com>

yarn.lock

@@ -2696,15 +2696,10 @@ copy-props@^2.0.1:
     each-props "^1.3.0"
     is-plain-object "^2.0.1"
 
-core-js@^2.2.0, core-js@^2.4.0:
-  version "2.5.5"
-  resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.5.5.tgz#b14dde936c640c0579a6b50cabcc132dd6127e3b"
-  integrity sha1-sU3ek2xkDAV5prUMq8wTLdYSfjs=
-
-core-js@^2.5.7:
-  version "2.5.7"
-  resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.5.7.tgz#f972608ff0cead68b841a16a932d0b183791814e"
-  integrity sha512-RszJCAxg/PP6uzXVXL6BsxSXx/B05oJAQ2vkJRjyjrEcNVycaqOmNb5OTxZPE3xa5gwZduqza6L9JOCenh/Ecw==
+core-js@^2.2.0, core-js@^2.4.0, core-js@^2.5.7:
+  version "2.6.4"
+  resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.4.tgz#b8897c062c4d769dd30a0ac5c73976c47f92ea0d"
+  integrity sha512-05qQ5hXShcqGkPZpXEFLIpxayZscVD2kuMBZewxiIPPEagukO4mqgPA9CWhUvFBJfy3ODdK2p9xyHh7FTU9/7A==
 
 core-util-is@1.0.2, core-util-is@~1.0.0:
   version "1.0.2"