Update polyserve requirement

Updates the requirements on [polyserve](https://github.com/Polymer/tools) to permit the latest version.
- [Release notes](https://github.com/Polymer/tools/releases)
- [Commits](https://github.com/Polymer/tools/commits/polyserve@0.27.13

)

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