Update clientlibs.md
Update clientlibs.md

https://github.com/siimon/prom-client seems like the more active and more feature complete project
vic3lord/docs,tcolgate/docs,tcolgate/docs,open-falcon/open-falcon.github.io,vic3lord/docs,du2016/prometheus-docs,prometheus/docs,tcolgate/docs,chosenken/docs,Cepave/openfalcon.io,pdbogen/docs,pdbogen/docs,ddfreyne/prometheus-docs,open-falcon/open-falcon.github.io,ddfreyne/prometheus-docs,prometheus/docs,open-falcon/open-falcon.github.io,pdbogen/docs,prometheus/docs,chosenken/docs,ddfreyne/prometheus-docs,chosenken/docs,du2016/prometheus-docs,vic3lord/docs,ddfreyne/prometheus-docs,Cepave/openfalcon.io,Cepave/openfalcon.io,du2016/prometheus-docs,chosenken/docs