build(deps-dev): bump rollup from 2.19.0 to 2.20.0 (vuejs#1537)

Author: dependabot-preview[bot]

yarn.lock

@@ -6202,9 +6202,9 @@ rollup-pluginutils@^2.3.1:
     estree-walker "^0.6.1"
 
 rollup@^2.16.1:
-  version "2.19.0"
-  resolved "https://registry.yarnpkg.com/rollup/-/rollup-2.19.0.tgz#6484868882281552b0dc33aa5bc5b36a9c920452"
-  integrity sha512-nny5Vs4jwY3vbQAXgOyU4ZDZqLvMKm/umnsVry/demVL6ve8ke1XhdpYE0eiWencASmx/qFPw6pP8P7MLJl9XA==
+  version "2.20.0"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-2.20.0.tgz#7456fed8424a5247954958751642e9fdd0ad7485"
+  integrity sha512-hkbp//ne1om8+PQRpd81zk0KDvbJxkLZdZJh1ZNxjd1EkI0H1TmYuHqqXx88yciS+5YnMom3geubQjTeeUnNNw==
   optionalDependencies:
     fsevents "~2.1.2"