minor #1095 Bump acorn from 6.4.0 to 6.4.1 (dependabot[bot])

This PR was merged into the master branch.

Discussion
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Bump acorn from 6.4.0 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.4.0 to 6.4.1.
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/acornjs/acorn/commit/9a2e9b6678e243d66846b91179d650d28453e70c"><code>9a2e9b6</code></a> Mark version 6.4.1</li>
<li><a href="https://github.com/acornjs/acorn/commit/90a9548ea0ce351b54f956e2c4ed27cca9631284"><code>90a9548</code></a> More rigorously check surrogate pairs in regexp validator</li>
<li>See full diff in <a href="https://github.com/acornjs/acorn/compare/6.4.0...6.4.1">compare view</a></li>
</ul>
</details>
<br />

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Commits
-------

f3c573c Bump acorn from 6.4.0 to 6.4.1

Author: javiereguiluz

yarn.lock

@@ -887,9 +887,9 @@ accepts@~1.3.4, accepts@~1.3.5, accepts@~1.3.7:
     negotiator "0.6.2"
 
 acorn@^6.2.1:
-  version "6.4.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.0.tgz#b659d2ffbafa24baf5db1cdbb2c94a983ecd2784"
-  integrity sha512-gac8OEcQ2Li1dxIEWGZzsp2BitJxwkwcOm0zHAJLcPJaVvm58FRnk6RkuLRpU1EujipU2ZFODv2P9DLMfnV8mw==
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
 [email protected]:
   version "2.0.0"