Raise minimum tested compiler to rust 1.80

Required by rayon.

    error: rustc 1.79.0 is not supported by the following packages:
      [email protected] requires rustc 1.80
      [email protected] requires rustc 1.80
      [email protected] requires rustc 1.80
      [email protected] requires rustc 1.80
    Either upgrade rustc or select compatible dependency versions with
    `cargo update <name>@<current-ver> --precise <compatible-ver>`
    where `<compatible-ver>` is the latest version supporting rustc 1.79.0

Author: dtolnay

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [1.67.0, stable, beta]
+        rust: [1.80.0, stable, beta]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v4