Pin pynn-brainscales to new version

I forgot to pin the version to the newly introduced rc2… spack decided to keep the old one → enforce new version.

mentioned in merge request !20 (merged)

mentioned in commit 18509729

merged

I merged it.

I was careless by accident it says that the source branch was deleted (do not know if i can get it back).
I hope i did not cause any issues. Sorry!

Source branch → don't care ;)…

Thx!

@emuller It failed! check logs from attached filepynn-brainscales-error.txt