fix: `LedgerStarknetApp` method privacy #560

Job	Run time
Build C++ integration example	1m 12s
Build starknet-curve features	8s
Build starknet-crypto-codegen features	24s
Build starknet-crypto features	25s
Build starknet-core features	56s
Build starknet-providers features	1m 5s
Build starknet-signers features	53s
Build starknet-accounts features	1m 10s
Build starknet-contract features	1m 12s
Build starknet-macros features	25s
Build starknet features	1m 42s
	9m 32s

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