Golf the proof of `Contiguous5.contiguous1_of_hasAntitoneBasis_le_cofinite`

[CoolRmal]

This theorem proves that contiguous5 implies contiguous1 under the assumption that the filter has an antitone basis and ≤ cofinite. It can be found in #10 in line 167.

This proof is generated by codex and needs to be golfed.