samples: subsys: updatehub: remove PSA overlay and test case

Updatehub now only use PSA Crypto API for crypto support and it
automatically enables Mbed TLS when TF-M is not available in the build,
so there is no need for neither a specific test case for PSA nor
the overlay file.

Signed-off-by: Valerio Setti <vsetti@baylibre.com>
2 files changed