1. - [x] Mandatory Add the required version to the Fix version/s field.
2. - [x] Mandatory Choose the type of documentation change.
      - [ ] New topic in an existing section or new section
      - [x] Update to an existing topic (pretty much anywhere PlacementRule is referenced in https://github.com/stolostron/rhacm-docs/tree/2.9_stage/governance)
3. - [x] Mandatory for GA content:
       - [ ] Add steps and/or other important conceptual information here: 
       - [ ] Add Required access level for the user to complete the task here:
       - [ ] Add verification at the end of the task, how does the user verify success (a command to run or a result to see?)
       - [x] Add link to dev story here: ACM-9052
4. - [ ] Mandatory for bugs: What is the diff? Clearly define what the problem is, what the change is, and link to the current documentation:

Update references from PlacementRule to Placement for GRC.
Draft PR, for review once 2.10_stage is open: https://github.com/stolostron/rhacm-docs/pull/6060