Offer no Replay for a delivery to a deleted target (closes #387)

The event log offered Replay on a delivery whose target was deleted,
and the refusal told the operator to recreate the target and replay.
That cannot work: a recreated target is a new one the old delivery
does not name, so the replay is refused again. The Replay button is
now left off such a delivery, whose row already names the target as
deleted, and the refusal a page left open can still reach now points
to Resubmit, which sends the event to the webhook's currently active
targets.

Model: opus-5-5

internal/handlers/notice.go

@@ -66,7 +66,8 @@ func noticeFor(r *http.Request) *notice {
 		},
 		replayTargetDeleted: {
 			Text: "Not replayed: the target this delivery was for " +
-				"has been deleted. Recreate the target, then replay.",
+				"has been deleted. Use Resubmit to send the event " +
+				"to the webhook's currently active targets.",
 			Failed: true,
 		},
 		replayTargetMissing: {