Bump acorn from 7.1.0 to 7.3.1

Bumps [acorn](https://github.com/acornjs/acorn) from 7.1.0 to 7.3.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/7.1.0...7.3.1)

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

package-lock.json

@@ -33,9 +33,9 @@
       }
     },
     "acorn": {
-      "version": "7.1.0",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.1.0.tgz",
-      "integrity": "sha512-kL5CuoXA/dgxlBbVrflsflzQ3PAas7RYZB52NOm/6839iVYJgKMJ3cQJD+t2i5+qFa8h3MDpEOJiS64E8JLnSQ=="
+      "version": "7.3.1",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.3.1.tgz",
+      "integrity": "sha512-tLc0wSnatxAQHVHUapaHdz72pi9KUyHjq5KyHjGg9Y8Ifdc79pTh2XvI6I1/chZbnM7QtNKzh66ooDogPZSleA=="
     },
     "ajv": {
       "version": "6.10.2",