Documentation: rename "Rookie guide" to "tutorial"

We generally try to stay away from ascribing attributes to (future)
devs. "Rookie guide" refers to the reader, while "tutorial" refers
to the material.

In the same spirit, move from "lessons" to "parts". It's not school :-)

Change-Id: I11a69a2a05ba9a0bc48f8bf62463d9585da043ec
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35425
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lance Zhao <lance.zhao@gmail.com>
Reviewed-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

Documentation/mainboard/supermicro/x10slm-f.md

@@ -12,7 +12,7 @@ Please see :doc:`../../northbridge/intel/haswell/mrc.bin`.
 
 ```eval_rst
 If you haven't already, build the coreboot toolchain as described in
-:doc:`../../lessons/lesson1`.
+:doc:`../../tutorial/part1`.
 ```
 
 A fully working image should be possible so long as you have the