Bump acorn from 5.7.3 to 5.7.4 in /client

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]

client/package-lock.json

@@ -941,8 +941,8 @@ acorn-walk@^6.0.1:
   resolved "https://registry.yarnpkg.com/acorn-walk/-/acorn-walk-6.1.0.tgz#c957f4a1460da46af4a0388ce28b4c99355b0cbc"
 
 acorn@^5.0.0, acorn@^5.0.3, acorn@^5.5.3, acorn@^5.6.0, acorn@^5.6.2, acorn@^5.7.1:
-  version "5.7.3"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.3.tgz#67aa231bf8812974b85235a96771eb6bd07ea279"
+  version "5.7.4"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.4.tgz#3e8d8a9947d0599a1796d10225d7432f4a4acf5e"
 
 acorn@^6.0.1:
   version "6.0.2"