libyang MAINTENANCE headers includes cleanup

iwyu_tool.py used
diff --git a/src/tree_data.c b/src/tree_data.c
index fbbeed0..199ae17 100644
--- a/src/tree_data.c
+++ b/src/tree_data.c
@@ -37,7 +37,7 @@
 #include "parser_data.h"
 #include "parser_internal.h"
 #include "path.h"
-#include "plugins_exts.h"
+#include "plugins.h"
 #include "plugins_exts_metadata.h"
 #include "plugins_internal.h"
 #include "plugins_types.h"