kconfig: modules: Remove redundant MBEDTLS dep on. TLS menu

Kconfig.tls-generic is already 'source'd within an 'if MBEDTLS' in
modules/Kconfig.mbedtls (the 'if' covers most of the file).

Flagged by https://github.com/zephyrproject-rtos/ci-tools/pull/128

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Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>