Fix flaky tests

Some tests were failing due to mismatch in Score in ZSetEntry.
Changed ZSetEntry Score to float64 type so that we can use
cmpopts.EquateApprox to allow for margin when comparing.

internal/asynqtest/asynqtest.go

@@ -20,7 +20,7 @@ import (
 // ZSetEntry is an entry in redis sorted set.
 type ZSetEntry struct {
 	Msg   *base.TaskMessage
-	Score int64
+	Score float64
 }
 
 // SortMsgOpt is a cmp.Option to sort base.TaskMessage for comparing slice of task messages.
@@ -245,7 +245,7 @@ func getZSetEntries(tb testing.TB, r *redis.Client, zset string) []ZSetEntry {
 	for _, z := range data {
 		entries = append(entries, ZSetEntry{
 			Msg:   MustUnmarshal(tb, z.Member.(string)),
-			Score: int64(z.Score),
+			Score: z.Score,
 		})
 	}
 	return entries