feat doxygen: enable multithread generation

commit_hash:3f29a3d8d8bba16beca61934fed7d06a18881b68

Author: ivan-skryabin

scripts/docs/doxygen.conf

@@ -530,7 +530,7 @@ LOOKUP_CACHE_SIZE      = 0
 # DOT_NUM_THREADS setting.
 # Minimum value: 0, maximum value: 32, default value: 1.
 
-NUM_PROC_THREADS       = 1
+NUM_PROC_THREADS       = 0
 
 # If the TIMESTAMP tag is set different from NO then each generated page will
 # contain the date or date and time when the page was generated. Setting this to