Fix for Prometheus documentation

Closes-Bug: #2102239
Change-Id: Ia8e551c62fc5d2d775098026d5d85611b81934fc
Signed-off-by: Rafal Lewandowski <rafal@stackhpc.com>
(cherry picked from commit ef7b067)

Author: g0rgamesh

doc/source/reference/logging-and-monitoring/prometheus-guide.rst

@@ -239,7 +239,7 @@ For example:
   :caption: ``/etc/kolla/globals.yml``
 
   prometheus_node_exporter_targets_extra:
-    - target: http://10.0.0.1:1234
+    - target: 10.0.0.1:1234
       labels:
         instance: host1