fix(integration): Use RequestFulfilled events instead of querying the purchase state

Author: emizzle

tests/integration/30_minutes/testproofs.nim

@@ -118,7 +118,7 @@ marketplacesuite(name = "Simulate invalid proofs", stopOnRequestFail = false):
       .some,
     ):
     let client0 = clients()[0].client
-    let expiry = 10.periods
+    let expiry = 15.periods
     let duration = expiry + 10.periods
 
     let data = await RandomChunker.example(blocks = blocks)