IGNITE-22917 Remove GridDhtLockRequest#nearKeys

GridDhtLockRequest#addNearKey(KeyCacheObject) usage was removed in commit in February 2015 [1]. Thus, this method seems to be useless.

Some related code in GridDhtTransactionalCacheAdapter, GridNearTransactionalCache, etc. was removed too because it became redundant.

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apache / ignite