[9.18] fix: dev: Remove unused <openssl/{hmac,engine}.h> headers from OpenSSL shims

The <openssl/{hmac,engine}.h> headers were unused and including the
<openssl/engine.h> header might cause build failure when OpenSSL
doesn't have Engines support enabled.

See https://fedoraproject.org/wiki/Changes/OpensslDeprecateEngine

Backport of MR !9593

Merge branch 'backport-bind-9.20-openssl-engine-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!9645

lib/isc/openssl_shim.c

@@ -16,9 +16,7 @@
 #include <string.h>
 
 #include <openssl/crypto.h>
-#include <openssl/engine.h>
 #include <openssl/evp.h>
-#include <openssl/hmac.h>
 #include <openssl/opensslv.h>
 #include <openssl/ssl.h>
 

lib/isc/openssl_shim.h

@@ -14,9 +14,7 @@
 #pragma once
 
 #include <openssl/crypto.h>
-#include <openssl/engine.h>
 #include <openssl/evp.h>
-#include <openssl/hmac.h>
 #include <openssl/opensslv.h>
 #include <openssl/ssl.h>