[purchasing] Remove Purchase.selected

There no longer exists a single host that
is selected for a contract.

codex/purchasing.nim

@@ -21,7 +21,6 @@ type
     market: Market
     clock: Clock
     request*: StorageRequest
-    selected*: ?Address
   PurchaseTimeout* = Timeout
 
 const DefaultProofProbability = 100.u256
@@ -77,10 +76,7 @@ proc run(purchase: Purchase) {.async.} =
       done.complete()
     let request = purchase.request
     let subscription = await market.subscribeFulfillment(request.id, callback)
-    try:
     await done
-      purchase.selected = await market.getHost(request.id)
-    finally:
     await subscription.unsubscribe()
 
   proc withTimeout(future: Future[void]) {.async.} =

codex/rest/json.nim

@@ -44,5 +44,4 @@ func `%`*(purchase: Purchase): JsonNode =
     "finished": purchase.finished,
     "error": purchase.error.?msg,
     "request": purchase.request,
-    "selected": purchase.selected
   }

tests/testIntegration.nim

@@ -103,5 +103,4 @@ ethersuite "Integration tests":
     let purchase = waitFor upload().buy().finish()
 
     check purchase["error"].getStr == ""
-    check purchase["selected"].getStr == $accounts[1]
     check available().len == 0