skipping slot 1 sync committee check e2e (#16145)

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**What type of PR is this?**

Tests

**What does this PR do? Why is it needed?**

```

--- PASS: TestEndToEnd_MinimalConfig/chain_started (0.50s)
--
--- PASS: TestEndToEnd_MinimalConfig/finished_syncing_0 (0.00s)
--- PASS: TestEndToEnd_MinimalConfig/all_nodes_have_same_head_0 (0.00s)
--- PASS: TestEndToEnd_MinimalConfig/validators_active_epoch_0 (0.00s)
--- FAIL: TestEndToEnd_MinimalConfig/validator_sync_participation_0 (0.01s)
--- PASS: TestEndToEnd_MinimalConfig/peers_connect_epoch_0 (0.11s)


```
This PR attempts to reduce flakes on validator sync participation
failures by skipping the first slot of the block after startup

**Which issues(s) does this PR fix?**

Fixes #

**Other notes for review**

**Acknowledgements**

- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description with sufficient context for reviewers
to understand this PR.
- [x] I have tested that my changes work as expected and I added a
testing plan to the PR description (if applicable).

changelog/james-prysm_skip-e2e-slot1-check.md

@@ -0,0 +1,3 @@
+### Changed
+
+- e2e sync committee evaluator now skips the first slot after startup, we already skip the fork epoch for checks here, this skip only applies on startup, due to altair always from 0 and validators need to warm up.

testing/endtoend/evaluators/validator.go

@@ -262,6 +262,11 @@ func validatorsSyncParticipation(_ *types.EvaluationContext, conns ...*grpc.Clie
 			// Skip fork slot.
 			continue
 		}
+		// Skip slot 1 at genesis - validators need time to ramp up after chain start.
+		// This is a startup timing issue, not a fork transition issue.
+		if b.Block().Slot() == 1 {
+			continue
+		}
 		expectedParticipation := expectedSyncParticipation
 		switch slots.ToEpoch(b.Block().Slot()) {
 		case params.BeaconConfig().AltairForkEpoch: