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](acornjs/acorn@5.7.3...5.7.4)

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

Author: dependabot[bot]

yarn.lock

@@ -990,8 +990,8 @@ acorn-dynamic-import@^3.0.0:
     acorn "^5.0.0"
 
 acorn@^5.0.0, acorn@^5.3.0, acorn@^5.6.2, acorn@^5.7.1:
-  version "5.7.3"
-  resolved "http://registry.npm.taobao.org/acorn/download/acorn-5.7.3.tgz#67aa231bf8812974b85235a96771eb6bd07ea279"
+  version "5.7.4"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.4.tgz#3e8d8a9947d0599a1796d10225d7432f4a4acf5e"
 
 address@^1.0.3:
   version "1.0.3"