Bump acorn from 5.7.3 to 5.7.4 in /src/main/jhipster

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]

src/main/jhipster/yarn.lock

@@ -522,15 +522,11 @@ acorn-dynamic-import@^3.0.0:
   dependencies:
     acorn "^5.0.0"
 
-acorn@^5.0.0:
+acorn@^5.0.0, acorn@^5.2.1:
   version "5.7.4"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.4.tgz#3e8d8a9947d0599a1796d10225d7432f4a4acf5e"
   integrity sha512-1D++VG7BhrtvQpNbBzovKNc1FLGGEE/oGe7b9xJm/RFHMBeUaUGpluV9RLjZa47YFdPcDAenEYuq9pQPcMdLJg==
 
-acorn@^5.2.1:
-  version "5.7.3"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.3.tgz#67aa231bf8812974b85235a96771eb6bd07ea279"
-
 adler-32@~1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/adler-32/-/adler-32-1.2.0.tgz#6a3e6bf0a63900ba15652808cb15c6813d1a5f25"