Update postcss-flexbugs-fixes requirement to 3.3.0 in /services/client

Updates the requirements on [postcss-flexbugs-fixes](https://github.com/luisrudge/postcss-flexbugs-fixes) to permit the latest version.
- [Release notes](https://github.com/luisrudge/postcss-flexbugs-fixes/releases)
- [Changelog](https://github.com/luisrudge/postcss-flexbugs-fixes/blob/master/CHANGELOG.md)
- [Commits](https://github.com/luisrudge/postcss-flexbugs-fixes/commits)

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

Author: dependabot-support

services/client/package.json

@@ -21,7 +21,7 @@
     "jsonwebtoken": "^8.2.0",
     "moment": "^2.19.1",
     "object-assign": "4.1.1",
-    "postcss-flexbugs-fixes": "3.2.0",
+    "postcss-flexbugs-fixes": "3.3.0",
     "postcss-loader": "2.1.4",
     "promise": "8.0.1",
     "prop-types": "^15.6.0",