Improve readability of absent() documentation (#711)
Improve readability of absent() documentation (#711)

This is just swapping two paragraphs and moves the explanation of the
example after the example itself.
du2016/prometheus-docs,chosenken/docs,prometheus/docs,chosenken/docs,du2016/prometheus-docs,chosenken/docs,ddfreyne/prometheus-docs,du2016/prometheus-docs,prometheus/docs,chosenken/docs,prometheus/docs,ddfreyne/prometheus-docs,ddfreyne/prometheus-docs,ddfreyne/prometheus-docs