OCM. federated connection is not dropped when one of the users deletes the connection

[ScharfViktor]

Web UI 10.3.0
Ocis: 6.5.0

Steps:
Given using server "LOCAL"
And "Alice" has generated invitation
And using server "REMOTE"
And "Brian" has accepted invitation
And using server "LOCAL"
When "Alice" deletes federation connection with user "Brian"

Actual:
Alice cannot longer find and share to Brian - correct
but Brian can find and share to Alice

Expected: both users cannot find and share with each other

[butonic]

not covered by the OCM spec AFAICT: created cs3org/OCM-API#147

[butonic]

decerased priority because this is not part of the spec, yet.