Do not expose the "Mute Notifications" sidebar menu entry when the underlying Editor for that object type does not support muting notifications (means: creating a transaction of type "core:edge") at all.
This avoids a disappointing PhabricatorApplicationTransactionStructureException after two clicks.
Disabling the menu entry while still exposing it makes no sense here as the user could never get it enabled anyway.
EXCEPTION: (PhabricatorApplicationTransactionStructureException) Attempting to apply a transaction (of class "PhabricatorFileTransaction", with type "core:edge") which has not been constructed correctly: Transaction has type "core:edge", but that transaction type is not supported by this editor (PhabricatorFileEditor). at [<phorge>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:1830]
EXCEPTION: (PhabricatorApplicationTransactionStructureException) Attempting to apply a transaction (of class "LegalpadTransaction", with type "core:edge") which has not been constructed correctly: Transaction has type "core:edge", but that transaction type is not supported by this editor (LegalpadDocumentEditor). at [<phorge>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:1830]
Closes T15378