Add QT_REQUIRE_CONFIG(ssl) to pre-shared key authenticator

As it's done (albeit in old-style there) in other public QSsl-classes.

Task-number: QTBUG-70604
Change-Id: If3cd9da0e8f8378fd29a80215cd889e459aa7bce
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/network/ssl/qsslpresharedkeyauthenticator.h

@@ -45,6 +45,8 @@
 #include <QtCore/QSharedDataPointer>
 #include <QtCore/QMetaType>
 
+QT_REQUIRE_CONFIG(ssl);
+
 QT_BEGIN_NAMESPACE
 
 class QSslPreSharedKeyAuthenticatorPrivate;