keys: rename `show` to `secret` #2148

Job	Run time
build (stellar-cli, stellar, ubuntu-20.04, x86_64-unknown-linux-gnu)	14m 29s
build (stellar-cli, stellar, ubuntu-20.04, aarch64-unknown-linux-gnu)	15m 32s
build (stellar-cli, stellar, macos-14, aarch64-apple-darwin)	8m 11s
build (stellar-cli, stellar, macos-14, x86_64-apple-darwin)	10m 10s
build (stellar-cli, stellar, windows-latest, x86_64-pc-windows-msvc, .exe)	21m 10s
installer	41s
	1h 10m 13s

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