fix: flaky test_bootstrap_from_snapshot

Summary

• fix: flaky test_bootstrap_from_snapshot

This check was too strict: assert i2.raft_first_index() == i1.raft_first_index() + 2

This is because governor can manage to apply more than 2 entries after log was compacted, so we can't rely on this strict difference of 2 commits. For example in this log 3 entries were applied: #1127 (comment 111700)

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• Close #1127 (closed)
• Cherry-pick to: none
• Docs follow-up: not necessary
• Changelog is updated