openssl: Remove checks and legacy compatibility code for OpenSSL < 1.0.2

More of this code was already removed with previous commits.

While versions < 1.1.1 are not officially supported anymore, 1.0.2 might
still be in use because before 3.x that was the latest version with
official FIPS support (OpenSSL apparently also provides extended commercial
support for it).

src/libstrongswan/plugins/openssl/openssl_aead.c

@@ -15,8 +15,6 @@
 
 #include <openssl/opensslv.h>
 
-#if OPENSSL_VERSION_NUMBER >= 0x1000100fL
-
 #include "openssl_aead.h"
 
 #include <openssl/evp.h>
@@ -363,5 +361,3 @@ aead_t *openssl_aead_create(encryption_algorithm_t algo,
 
 	return &this->public;
 }
-
-#endif /* OPENSSL_VERSION_NUMBER */