conditional include of sl_matter_ota_config.h (#35724)

diff --git a/examples/platform/silabs/OTAConfig.h b/examples/platform/silabs/OTAConfig.h
index c97202e..07d6103 100644
--- a/examples/platform/silabs/OTAConfig.h
+++ b/examples/platform/silabs/OTAConfig.h
@@ -29,7 +29,7 @@
 #include <platform/silabs/OTAImageProcessorImpl.h>
 #endif
 
-#if (SL_MATTER_GN_BUILD == 0)
+#if (SL_MATTER_GN_BUILD == 0) && defined(SILABS_OTA_ENABLED)
 #include "sl_matter_ota_config.h"
 #endif