Bump acorn from 5.7.3 to 5.7.4

Bumps [acorn](https://github.com/acornjs/acorn) from 5.7.3 to 5.7.4.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/5.7.3...5.7.4)

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

package-lock.json

@@ -927,9 +927,9 @@
       "dev": true
     },
     "acorn": {
-      "version": "6.3.0",
+      "version": "6.4.1",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.3.0.tgz",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.4.1.tgz",
-      "integrity": "sha512-/czfa8BwS88b9gWQVhc8eknunSA2DoJpJyTQkhheIf5E48u1N0R4q/YxxsAeqRrmK9TQ/uYfgLDfZo91UlANIA==",
+      "integrity": "sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==",
       "dev": true
     },
     "acorn-globals": {
@@ -4660,9 +4660,9 @@
       },
       "dependencies": {
         "acorn": {
-          "version": "5.7.3",
+          "version": "5.7.4",
-          "resolved": "https://registry.npmjs.org/acorn/-/acorn-5.7.3.tgz",
+          "resolved": "https://registry.npmjs.org/acorn/-/acorn-5.7.4.tgz",
-          "integrity": "sha512-T/zvzYRfbVojPWahDsE5evJdHb3oJoQfFbsrKM7w5Zcs++Tr257tia3BmMP8XYVjp1S9RZXQMh7gao96BlqZOw==",
+          "integrity": "sha512-1D++VG7BhrtvQpNbBzovKNc1FLGGEE/oGe7b9xJm/RFHMBeUaUGpluV9RLjZa47YFdPcDAenEYuq9pQPcMdLJg==",
           "dev": true
         }
       }