MINOR: contrib/prometheus-exporter: use stats desc when possible followup

Remove remaining descrition which are common to stats.c.

This patch is a followup of commit
82b2ce2f967d967139adb7afab064416fadad615 ("MINOR:
contrib/prometheus-exporter: use stats desc when possible"). I probably
messed up with one of my rebase because I'm pretty sure I removed them
at some point, but who knows what happened.

Signed-off-by: William Dauchy <wdauchy@gmail.com>
1 file changed