Add more missing calls to nom::combinator::complete

[tomaka]

Similar to #2340
There's another code pattern where I don't call finish but I manually match the error and use unreachable!(). This PR fixes it as well.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼────────────────────────────────────────────────────────────────────────────────────
        +170 ┊ <F as nom::internal::Parser<I,O,E>>::parse::h5d0ac7a87023dd6b
        +170 ┊ <F as nom::internal::Parser<I,O,E>>::parse::h8d4ee6d7d9a70fdd
        +134 ┊ <F as nom::internal::Parser<I,O,E>>::parse::h99c027afdf604af8
          +8 ┊ smoldot::network::protocol::block_request::decode_block_response::h35182f468af63c22
        +767 ┊ Σ [4 Total Rows]

[melekes]

👍