Bump acorn from 6.0.1 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.0.1 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.0.1...6.4.1)

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

Author: dependabot[bot]

package-lock.json

@@ -31,7 +31,7 @@
     "shift-regexp-acceptor": "2.0.2"
   },
   "devDependencies": {
-    "acorn": "6.0.1",
+    "acorn": "6.4.1",
     "angular": "1.7.4",
     "babel-cli": "6.26.0",
     "babel-core": "6.26.3",