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>

yarn.lock

@@ -1131,16 +1131,11 @@ acorn-walk@^6.0.1:
   integrity sha512-ugTb7Lq7u4GfWSqqpwE0bGyoBZNMTok/zDBXxfEG0QM50jNlGhIWjRC1pPN7bvV1anhF+bs+/gNcRw+o55Evbg==
 
 acorn@^5.5.3:
-  version "5.7.3"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.3.tgz#67aa231bf8812974b85235a96771eb6bd07ea279"
-  integrity sha512-T/zvzYRfbVojPWahDsE5evJdHb3oJoQfFbsrKM7w5Zcs++Tr257tia3BmMP8XYVjp1S9RZXQMh7gao96BlqZOw==
+  version "5.7.4"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.4.tgz#3e8d8a9947d0599a1796d10225d7432f4a4acf5e"
+  integrity sha512-1D++VG7BhrtvQpNbBzovKNc1FLGGEE/oGe7b9xJm/RFHMBeUaUGpluV9RLjZa47YFdPcDAenEYuq9pQPcMdLJg==
 
-acorn@^6.0.1:
-  version "6.0.4"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.0.4.tgz#77377e7353b72ec5104550aa2d2097a2fd40b754"
-  integrity sha512-VY4i5EKSKkofY2I+6QLTbTTN/UvEQPCo6eiwzzSaSWfpaDhOmStMCMod6wmuPciNq+XS0faCglFu2lHZpdHUtg==
-
-acorn@^6.0.7:
+acorn@^6.0.1, acorn@^6.0.7:
   version "6.1.0"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.1.0.tgz#b0a3be31752c97a0f7013c5f4903b71a05db6818"
   integrity sha512-MW/FjM+IvU9CgBzjO3UIPCE2pyEwUsoFl+VGdczOPEdxfGFjuKny/gN54mOuX7Qxmb9Rg9MCn2oKiSUeW+pjrw==