build(deps): bump acorn from 6.2.0 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.2.0 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.2.0...6.4.1)

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

Author: dependabot[bot]

yarn.lock

@@ -72,8 +72,9 @@ acorn-jsx@^5.0.0:
   resolved "https://registry.yarnpkg.com/acorn-jsx/-/acorn-jsx-5.0.1.tgz#32a064fd925429216a09b141102bfdd185fae40e"
 
 acorn@^6.0.7:
-  version "6.2.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.2.0.tgz#67f0da2fc339d6cfb5d6fb244fd449f33cd8bbe3"
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
 ajv@^6.10.0, ajv@^6.9.1:
   version "6.10.1"