fix: add missing explicit lifetime in ExcelSubrange return type for rust 1.83 build - #353

  error: elided lifetime has a name
    --> columnq/src/table/excel.rs:48:10
     |
  41 | impl<'a> ExcelSubrange<'a> {
     |      -- lifetime `'a` declared here
  ...
  48 |     ) -> ExcelSubrange {
     |          ^^^^^^^^^^^^^ this elided lifetime gets resolved as `'a`
     |
  note: the lint level is defined here
    --> columnq/src/lib.rs:1:9
     |
  1  | #![deny(warnings)]
     |         ^^^^^^^^
     = note: `#[deny(elided_named_lifetimes)]` implied by `#[deny(warnings)]`