Some of the plugins for vCenter don’t offer an uninstaller.
To unregister a plugin from vCenter follow this method provided by a VMware KB:
Open a web browser and go to http://vcenterserver/mob
Click on Content
Click on ExtensionManager
Copy the name of the plugin you want to unregister
Click on UnregisterExtension
In the text field paste the text into the box and delete all but the part in quotes(e.g.com.emc.EMCStoragePlugin)
Refresh the browser and the plugin should be gone from the list
Reconnect to vCenter using the client and the plugin should be gone from Plug-ins-> Manage Plugins list.