Resolve Rust 1.75's new get_first clippy lint

[dtolnay]

CI in #1905 is failing because the default rustc available in GitHub's runner got bumped from 1.74 to 1.75 recently.

error: accessing first element with `values.get(0)`
  --> src/i18n.rs:20:31
   |
20 |             let email = match values.get(0) {
   |                               ^^^^^^^^^^^^^ help: try: `values.first()`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#get_first
   = note: `-D clippy::get-first` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::get_first)]`

error: accessing first element with `values.get(0)`
  --> src/i18n.rs:30:30
   |
30 |             let text = match values.get(0) {
   |                              ^^^^^^^^^^^^^ help: try: `values.first()`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#get_first