fix(resharding) - fixing the resharding.py nayduck test (#10895)

The resharding nayduck test is
[flaky](https://nayduck.near.org/#/test_history/593017). I believe that
is because every now and then taking the state snapshot takes a long
time and the test breaks before snapshot is ready for resharding.

I went all the way to the following line and it seems like most of the
slowness is there. It's down to rocksdb at this point and I don't feel
like debugging it further so I'm just going to increase the epoch length
to give the test enough time to take the snapshot and finish resharding.

https://github.com/near/nearcore/blob/d4d1b82f39a57932eff0a7a28c5745b72915f848/core/store/src/db/rocksdb/snapshot.rs#L98

pytest/tests/sanity/resharding.py

@@ -23,7 +23,7 @@
 class ReshardingTest(ReshardingTestBase):
 
     def setUp(self) -> None:
-        super().setUp(epoch_length=5)
+        super().setUp(epoch_length=20)
 
     def test_resharding(self):
         logger.info("The resharding test is starting.")