Update dependency rollup to v1.15.6 (#539)

Author: renovate[bot]

package.json

@@ -76,7 +76,7 @@
     "react": "16.8.2",
     "react-dom": "16.8.2",
     "react-test-renderer": "16.8.6",
-    "rollup": "1.15.5",
+    "rollup": "1.15.6",
     "rollup-plugin-babel": "4.3.2",
     "rollup-plugin-commonjs": "10.0.0",
     "rollup-plugin-node-globals": "1.4.0",

yarn.lock

@@ -9188,10 +9188,10 @@ rollup-watch@4.3.1:
     require-relative "0.8.7"
     rollup-pluginutils "^2.0.1"
 
-rollup@1.15.5:
-  version "1.15.5"
-  resolved "https://registry.yarnpkg.com/rollup/-/rollup-1.15.5.tgz#1c1f7ef799d5b297aab6eb49ca7a6ab9c8aae6a0"
-  integrity sha512-Dix1YCY6BlsVK20SjQHBjKqxW2K+lqNr6BlCKxtdZuYqmUWLm8NzKHdrJyiFFjUO2hSI4wiC7apE+jAkDA3fEQ==
+rollup@1.15.6:
+  version "1.15.6"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-1.15.6.tgz#caf0ed28d2d78e3a59c1398e5a3695fb600a0ef0"
+  integrity sha512-s3Vn3QJQ5YVFfIG4nXoG9VdL1I37IZsft+4ZyeBhxE0df1kCFz9e+4bEAbR4mKH3pvBO9e9xjdxWPhhIp0r9ow==
   dependencies:
     "@types/estree" "0.0.39"
     "@types/node" "^12.0.8"