doc: Correct link to Prometheus docs

The link is to the `#http_sd_config` anchor in the prometheus config docs; that link only works without the trailing `/`.

This correction would ideally get backported to at least reef & squid.

Signed-off-by: Matthew Vernon <[email protected]>

Author: mcv21

doc/cephadm/services/monitoring.rst

@@ -279,7 +279,7 @@ definition and management of the embedded Prometheus service. The endpoint liste
 ``https://<mgr-ip>:8765/sd/`` (the port is
 configurable through the variable ``service_discovery_port``) and returns scrape target
 information in `http_sd_config format
-<https://prometheus.io/docs/prometheus/latest/configuration/configuration/#http_sd_config/>`_
+<https://prometheus.io/docs/prometheus/latest/configuration/configuration/#http_sd_config>`_
 
 Customers with external monitoring stack can use `ceph-mgr` service discovery endpoint
 to get scraping configuration. Root certificate of the server can be obtained by the