Remove dead deprecated get_transaction code path

While going through the deprecated markers in the codebase I noticed the whole get_transaction chain is dead code — nothing in production calls it anymore:

• StarknetData.Transaction() (starknetdata/starknetdata.go) — declared on the interface but never called
• Feeder.Transaction() (starknetdata/feeder/feeder.go) — only implements the above
• Client.Transaction() (clients/feeder/feeder.go) — hits the legacy get_transaction feeder gateway endpoint
• starknet.DeprecatedTransactionStatus (starknet/transaction.go) — only used by the method above

The only remaining references are the interface declarations, generated mocks, and a few tests that exercise the chain directly. On top of being unused, this is the last code path touching the legacy get_transaction endpoint, and it carries a //nolint:staticcheck escape in the feeder client.

Proposal: remove the method from both interfaces, drop the implementations and the DeprecatedTransactionStatus type, regenerate mocks, and clean up the tests. Happy to send a PR for this.

Start by reading the Transaction declarations and implementations in starknetdata/starknetdata.go, starknetdata/feeder/feeder.go, clients/feeder/feeder.go, and starknet/transaction.go, then inspect the generated mocks and tests that reference them. Done means the dead methods, DeprecatedTransactionStatus type, legacy endpoint path, mock references, and related tests are removed while the remaining tests pass.