README: add closing brace
README: add closing brace

Looks like the closing brace was missing. Fix this.
GoogleCloudPlatform/go-endpoints,k2wanko/go-endpoints,ritoon/go-endpoints,flowlo/go-endpoints,jonprice/go-endpoints,exchaos/go-endpoints,ceram1/go-endpoints,zombiezen/go-endpoints,belua/go-endpoints,rwl/endpoints