nmcs: remove nmcs_provider_*_get_type forward declaration

There is no need to avoid including the full header, they are small
headers with some GLib type system stuff and no more. Just include them
where they are needed.

src/nm-cloud-setup/nmcs-provider.c

@@ -3,6 +3,8 @@
 #include "libnm-client-aux-extern/nm-default-client.h"
 
 #include "nmcs-provider.h"
+#include "nmcs-provider-aliyun.h"
+#include "nmcs-provider-oci.h"
 
 #include "nm-cloud-setup-utils.h"
 

src/nm-cloud-setup/nmcs-provider.h

@@ -220,11 +220,4 @@ void nmcs_provider_get_config(NMCSProvider       *provider,
 NMCSProviderGetConfigResult *
 nmcs_provider_get_config_finish(NMCSProvider *provider, GAsyncResult *result, GError **error);
 
-/*****************************************************************************/
-
-/* Forward declare the implemented gtype getters so we can use it at a few places without requiring
- * to include the full header. The other parts of those headers should not be used aside where they
- * are necessary. */
-GType nmcs_provider_aliyun_get_type(void);
-
 #endif /* __NMCS_PROVIDER_H__ */