chore: fix sync handler parameter naming

[JonathanOppenheimer]

In subnet-evm: sync/handlers/stats/statstest/test_stats.go

In coreth: https://github.com/ava-labs/avalanchego/blob/master/graft/coreth/sync/handlers/stats/statstest/test_stats.go

[No action] Lets leave it for now since it's aligned with coreth, but m should have been updated t when this was originally updated to match naming conventions for receivers

Originally posted by @michaelkaplan13 in ava-labs/subnet-evm#1886 (comment)