add upper bounds on cstruct.4.0.0 due to sexplib removal

[avsm]

see #13748

[camelus]

☀️ All lint checks passed 5035cba

• These packages passed lint tests: charrua-core.0.10, charrua-core.0.11.0, charrua-core.0.11.1, charrua-core.0.11.2, charrua-core.0.12.0, charrua-core.0.8, charrua-core.0.9, protocol-9p.0.1, protocol-9p.0.10.0, protocol-9p.0.11.0, protocol-9p.0.11.1, protocol-9p.0.11.2, protocol-9p.0.11.3, protocol-9p.0.12.0, protocol-9p.0.12.1, protocol-9p.0.2, protocol-9p.0.3, protocol-9p.0.4.0, protocol-9p.0.5.0, protocol-9p.1.0.0, protocol-9p.1.0.1, protocol-9p.2.0.0

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☀️ Installability check (10884 → 10884)

[mseri]

I went through all of the changes, seems safe to merge. It cannot make things worse, if anything by merging we can reduce the ci load a bit

[avsm]

thanks!