B OpenNebula/one#6781: add issue 6781 in known issues file (#3194)

Author: jloboescalona2

source/intro_release_notes/release_notes/known_issues.rst

@@ -32,6 +32,9 @@ Sunstone
 
 - The `Update VM Configuration` dialog contains a bug which will result in a blank screen if one tries to update the configuration of a virtual machine with less than 2 total disks attached. The quickest workaround for this is to attach another minimal disk to the VM.
 
+- When deleting an element in the datatable. such as running the terminate in a VM, we recommend refreshing the window. as there is an error in the client code discussed in the following `issue <https://github.com/OpenNebula/one/issues/6781>`__.
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 Install Linux Graphical Desktop on KVM Virtual Machines
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