FIX: support labels with " and special chars

FIX: support labels with " and special chars

This upgrades the version of prom exporter to one that includes:

https://github.com/discourse/prometheus_exporter/commit/97994d57c1e24b7ecf8d4f8786895520710d268e

This is important cause in some rare case we could corrupt the prom payload

diff --git a/prometheus_exporter_version b/prometheus_exporter_version
index 2b7c5ae..f905682 100644
--- a/prometheus_exporter_version
+++ b/prometheus_exporter_version
@@ -1 +1 @@
-0.4.2
+0.4.7

GitHub sha: 3a874f4c