Bump acorn from 6.4.0 to 6.4.1 in /spec/dummy

Bumps [acorn](https://github.com/acornjs/acorn) from 6.4.0 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.4.0...6.4.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

spec/dummy/yarn.lock

@@ -1006,9 +1006,9 @@ accepts@~1.3.7:
     negotiator "0.6.2"
 
 acorn@^6.2.1:
-  version "6.4.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.0.tgz#b659d2ffbafa24baf5db1cdbb2c94a983ecd2784"
-  integrity sha512-gac8OEcQ2Li1dxIEWGZzsp2BitJxwkwcOm0zHAJLcPJaVvm58FRnk6RkuLRpU1EujipU2ZFODv2P9DLMfnV8mw==
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
 aggregate-error@^3.0.0:
   version "3.0.1"
@@ -4370,6 +4370,7 @@ matestack-ui-core@../../:
     link-module-alias "^1.2.0"
     v-runtime-template "^1.5.2"
     vue "^2.5.17"
+    vue-turbolinks "^2.1.0"
     vuex "^3.0.1"
     yarn "^1.22.0"
 
@@ -7524,7 +7525,14 @@ vm-browserify@^1.0.1:
   resolved "https://registry.yarnpkg.com/vm-browserify/-/vm-browserify-1.1.2.tgz#78641c488b8e6ca91a75f511e7a3b32a86e5dda0"
   integrity sha512-2ham8XPWTONajOR0ohOKOHXkm3+gaBmGut3SRuu75xLd/RRaY6vqgh8NBYYk7+RW3u5AtzPQZG8F10LHkl0lAQ==
 
-vue@^2.5.17:
+vue-turbolinks@^2.1.0:
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/vue-turbolinks/-/vue-turbolinks-2.1.0.tgz#fc7372d06d624aa3fb68231dc0b509719edc778f"
+  integrity sha512-Rgq9eUS2LgHVoSR58S0utW7g/aqLlVZ6uM7S1e02+xEUGKW1fqhUHQXea3p+cE59ldf+f3nz3Cc3HVO4MlrTFA==
+  dependencies:
+    vue "^2.2.4"
+
+vue@^2.2.4, vue@^2.5.17:
   version "2.6.11"
   resolved "https://registry.yarnpkg.com/vue/-/vue-2.6.11.tgz#76594d877d4b12234406e84e35275c6d514125c5"
   integrity sha512-VfPwgcGABbGAue9+sfrD4PuwFar7gPb1yl1UK1MwXoQPAw0BKSqWfoYCT/ThFrdEVWoI51dBuyCoiNU9bZDZxQ==