rust: fix mismatched_lifetime_syntaxes warning

rust: fix mismatched_lifetime_syntaxes warning

Fix new warning present in Rust 1.89.

warning: hiding a lifetime that's elided elsewhere is confusing
   --> src/ldap/types.rs:191:30
    = help: the same lifetime is referred to in inconsistent ways, making the signature confusing
    = note: `#[warn(mismatched_lifetime_syntaxes)]` on by default
help: use `'_` for type paths