Bump acorn from 6.2.1 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.2.1 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.2.1...6.4.1)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

yarn.lock

@@ -1875,16 +1875,11 @@ acorn-walk@^7.1.1:
   integrity sha512-wdlPY2tm/9XBr7QkKlq0WQVgiuGTX6YWPyRyBviSoScBuLfTVQhvwg6wJ369GJ/1nPfTLMfnrFIfjqVg6d+jQQ==
 
 acorn@^6.0.1, acorn@^6.2.1:
-  version "6.2.1"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.2.1.tgz#3ed8422d6dec09e6121cc7a843ca86a330a86b51"
-  integrity sha512-JD0xT5FCRDNyjDda3Lrg/IxFscp9q4tiYtxE1/nOzlKCk7hIRuYjhq1kCNkbPjMRMZuFq20HNQn1I9k8Oj0E+Q==
-
-acorn@^7.1.0:
-  version "7.1.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.0.tgz#949d36f2c292535da602283586c2477c57eb2d6c"
-  integrity sha512-kL5CuoXA/dgxlBbVrflsflzQ3PAas7RYZB52NOm/6839iVYJgKMJ3cQJD+t2i5+qFa8h3MDpEOJiS64E8JLnSQ==
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
-acorn@^7.1.1:
+acorn@^7.1.0, acorn@^7.1.1:
   version "7.1.1"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.1.tgz#e35668de0b402f359de515c5482a1ab9f89a69bf"
   integrity sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==