Update package.json, yarn.lock

package.json

@@ -9,7 +9,7 @@
     "@webassemblyjs/helper-module-context": "1.9.0",
     "@webassemblyjs/wasm-edit": "1.9.0",
     "@webassemblyjs/wasm-parser": "1.9.0",
-    "acorn": "^7.1.1",
+    "acorn": "^6.4.1",
     "ajv": "^6.10.2",
     "ajv-keywords": "^3.4.1",
     "chrome-trace-event": "^1.0.2",

yarn.lock

@@ -689,15 +689,10 @@ acorn@^5.5.3:
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.3.tgz#67aa231bf8812974b85235a96771eb6bd07ea279"
   integrity sha512-T/zvzYRfbVojPWahDsE5evJdHb3oJoQfFbsrKM7w5Zcs++Tr257tia3BmMP8XYVjp1S9RZXQMh7gao96BlqZOw==
 
-acorn@^6.0.1, acorn@^6.0.7:
-  version "6.4.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.0.tgz#b659d2ffbafa24baf5db1cdbb2c94a983ecd2784"
-  integrity sha512-gac8OEcQ2Li1dxIEWGZzsp2BitJxwkwcOm0zHAJLcPJaVvm58FRnk6RkuLRpU1EujipU2ZFODv2P9DLMfnV8mw==
-
-acorn@^7.0.0:
-  version "7.1.1"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.1.tgz#e35668de0b402f359de515c5482a1ab9f89a69bf"
-  integrity sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==
+acorn@^6.0.1, acorn@^6.0.7, acorn@^6.4.1:
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
 ajv-errors@^1.0.0:
   version "1.0.1"
@@ -4651,9 +4646,9 @@ nopt@3.x:
     abbrev "1"
 
 nopt@^4.0.1:
-  version "4.0.1"
-  resolved "https://registry.yarnpkg.com/nopt/-/nopt-4.0.1.tgz#d0d4685afd5415193c8c7505602d0d17cd64474d"
-  integrity sha1-0NRoWv1UFRk8jHUFYC0NF81kR00=
+  version "4.0.3"
+  resolved "https://registry.yarnpkg.com/nopt/-/nopt-4.0.3.tgz#a375cad9d02fd921278d954c2254d5aa57e15e48"
+  integrity sha512-CvaGwVMztSMJLOeXPrez7fyfObdZqNUK1cPAEzLHrTybIua9pMdmmPR5YwtfNftIOMv3DPUhFaxsZMNTQO20Kg==
   dependencies:
     abbrev "1"
     osenv "^0.1.4"