[config] Add HB_NO_OT_KERN, enabled by HB_MINI / HB_NO_LEGACY

Part of https://github.com/harfbuzz/harfbuzz/issues/1652
diff --git a/src/hb-config.hh b/src/hb-config.hh
index c1a15f8..e02694b 100644
--- a/src/hb-config.hh
+++ b/src/hb-config.hh
@@ -101,6 +101,7 @@
 
 #ifdef HB_NO_LEGACY
 #define HB_NO_FALLBACK_SHAPE
+#define HB_NO_OT_KERN
 #define HB_NO_OT_LAYOUT_BLACKLIST
 #define HB_NO_OT_SHAPE_FALLBACK
 #endif