metrics: Need to surround label value with double quotes

Signed-off-by: David Goulet <dgoulet@torproject.org>
9 jobs for relay-metrics-quick-fix in 21 minutes and 14 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #20766
debian-disable-dirauth

00:06:02

passed #20767
debian-disable-relay

00:05:24

passed #20762
debian-distcheck

00:08:04

passed #20763
debian-docs

00:02:51

passed #20761
debian-hardened

00:08:14

passed #20764
debian-integration

00:18:30

passed #20760
debian-minimal

00:06:18

passed #20768
debian-nss

00:05:06

passed #20765
debian-tracing

00:08:03