Correct improper use of 'labels' setting.
Correct improper use of 'labels' setting.

The 'labels' setting in the global configuration section has been renamed to 'external_labels' and now has changed semantics. Hence, the fix.
tcolgate/docs,open-falcon/open-falcon.github.io,prometheus/docs,chosenken/docs,prometheus/docs,vic3lord/docs,pdbogen/docs,du2016/prometheus-docs,Cepave/openfalcon.io,tcolgate/docs,pdbogen/docs,chosenken/docs,ddfreyne/prometheus-docs,chosenken/docs,tcolgate/docs,vic3lord/docs,pdbogen/docs,prometheus/docs,ddfreyne/prometheus-docs,du2016/prometheus-docs,vic3lord/docs,open-falcon/open-falcon.github.io,ddfreyne/prometheus-docs,ddfreyne/prometheus-docs,Cepave/openfalcon.io,open-falcon/open-falcon.github.io,du2016/prometheus-docs,chosenken/docs,Cepave/openfalcon.io