mosquitto_passwd.c: problematic use of OPENSSL_API_COMPAT

[dirkfeytons]

According to https://www.openssl.org/docs/man3.1/man7/OPENSSL_API_COMPAT.html the OPENSSL_API_COMPAT macro is expected to be set by the user on the compiler command line or at the top of a source file before any OpenSSL header is included.
The way it's used at

mosquitto/apps/mosquitto_passwd/mosquitto_passwd.c

Line 459 in 3923526

#if OPENSSL_VERSION_NUMBER < 0x10100000L || OPENSSL_API_COMPAT < 0x10100000L

can lead to an undesired build error: since OPENSSL_API_COMPAT is not defined in a standard Mosquitto build, the condition OPENSSL_API_COMPAT < 0x10100000L in the code will evaluate to true and the call to OpenSSL_add_all_digests() is included. However, when OpenSSL is built with no-deprecated then this symbol does not exist and the build fails.

The check should simply be removed from the code; only checking for OPENSSL_VERSION_NUMBER < 0x10100000L is sufficient.