Bump rimraf from 2.6.2 to 2.6.3

Bumps [rimraf](https://github.com/isaacs/rimraf) from 2.6.2 to 2.6.3.
- [Release notes](https://github.com/isaacs/rimraf/releases)
- [Commits](isaacs/rimraf@v2.6.2...v2.6.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package-lock.json

@@ -55,7 +55,7 @@
     "postcss-import": "^11.0.0",
     "postcss-loader": "^2.0.8",
     "postcss-url": "^7.2.1",
-    "rimraf": "^2.6.0",
+    "rimraf": "^2.6.3",
     "semver": "^5.3.0",
     "shelljs": "^0.7.6",
     "uglifyjs-webpack-plugin": "^1.1.1",