server `ShareValidationResult` has outdated Rust Docs

[plebhash]

overlooked in #1966

warning: unresolved link to `ShareValidationResult::ValidWithAcknowledgement`
  --> sv2/channels-sv2/src/server/share_accounting.rs:26:11
   |
26 | /// The [`ShareValidationResult::ValidWithAcknowledgement`] variant carries:
   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the enum `ShareValidationResult` has no variant or associated item named `ValidWithAcknowledgement`
   |
   = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default