chore: remove no-longer-relevant forks on dev

[huitseeker]

See :

• https://github.com/lurk-lab/arecibo/pull/277 and its integration into
• https://github.com/lurk-lab/arecibo/pull/279 (removing arecibo's pointer to blstrs, hence obsoleting the blstrs/ec-gpu forks)
• https://github.com/lurk-lab/arecibo/issues/332

[!NOTE] The target of this PR is dev, not main, intentionally.