Ambari does not support uninstall but you can effectively achieve the same thing by actually Stopping the Service and deleting it using API. Here is the links to the wiki page to do it using API:
https://cwiki.apache.org/confluence/display/AMBARI/Using+APIs+to+delete+a+service+or+all+host+components+on+a+host
If you are looking to move just the Metrics Collector, here is the steps to achieve the same:
https://cwiki.apache.org/confluence/display/AMBARI/Moving+Metrics+Collector+to+a+new+host