docs: fix broken paths to docs/devel/atomics.txt

With the move of some docs/ to docs/devel/ on ac06724a71,
a couple of references were not updated.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
3 files changed