Add note that OpenShift routes can't be accessed in a browser

Per this discussion on Slack https://coreos.slack.com/archives/G79AW9Q7R/p1654741944386019, we should mention that if you get OpenShift routes using oc -n openshift-monitoring get route and then try to open the route in a a web browser, you will see an Application not available error in the browser. This is a result of access to the 3rd-party Prometheus UI being removed from OCP.

We should add a note to https://docs.openshift.com/container-platform/4.10/monitoring/accessing-third-party-monitoring-uis-and-apis.html#accessing-third-party-monitoring-web-service-apis and say something along the lines of:

• "only the endpoints under the /api path can be accessed via OpenShift routes"
• if you try to access a route in a browser, you will get an Application not available error
• use the OCP web console instead of a web browser to access a route