Bump acorn from 6.3.0 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.3.0 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.3.0...6.4.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

yarn.lock

@@ -677,9 +677,9 @@ acorn-jsx@^5.0.0:
   integrity sha512-tMUqwBWfLFbJbizRmEcWSLw6HnFzfdJs2sOJEOwwtVPMoH/0Ay+E703oZz78VSXZiiDcZrQ5XKjPIUQixhmgVw==
 
 acorn@^6.0.7:
-  version "6.3.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.3.0.tgz#0087509119ffa4fc0a0041d1e93a417e68cb856e"
-  integrity sha512-/czfa8BwS88b9gWQVhc8eknunSA2DoJpJyTQkhheIf5E48u1N0R4q/YxxsAeqRrmK9TQ/uYfgLDfZo91UlANIA==
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
 ajv@^6.10.2, ajv@^6.9.1:
   version "6.10.2"