Fix monospace syntax on clusters/placement_managed.adoc

[evanstoner]

Red Hat Advanced Cluster Management for Kubernetes documentation issue

Product release(s)

• [ACM 2.3 GA]

Locations of the suggested changes?

Links to the topics that contain the suggested updates:

• https://github.com/open-cluster-management/rhacm-docs/blob/2.3_stage/clusters/placement_managed.adoc#placement-overview

Section:

• Placement overview

What are the suggested changes?

Line 26 contains:

`Placement'

but it should be:

`Placement`

to correctly format the monospace font.