Short-tag AEAD with the nominal length are encoded as nominal AEAD
Short-tag AEAD with the nominal length are encoded as nominal AEAD

`PSA_ALG_AEAD_WITH_SHORTENED_TAG(aead_alg, len) == aead_alg` when
`len == PSA_AEAD_TAG_LENGTH(aead_alg)`. So skip this case when testing
the printing of constants.

This fixes one test case due to the way arguments of
`PSA_ALG_AEAD_WITH_SHORTENED_TAG` are enumerated (all algorithms are tested
for a value of `len` which isn't problematic, and all values of `len` are
tested for one algorithm).

Signed-off-by: Gilles Peskine <f805f64266d288fc5467baa7be6cd0ff366f477b@arm.com>

Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls