Raise required compiler to rust 1.60

Required by reqwest 0.12.

    error: failed to select a version for the requirement `reqwest = "^0.12"`
    candidate versions found which didn't match: 0.11.23, 0.11.22, 0.11.21, ...
    location searched: crates.io index
    required by package `unsafe-libyaml-test-suite v0.0.0`

.github/workflows/ci.yml

@@ -37,7 +37,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [stable, beta, 1.56.0]
+        rust: [stable, beta, 1.60.0]
         include:
           - rust: nightly
             components: rustc-dev

Cargo.toml

@@ -18,7 +18,7 @@ include = [
 keywords = ["macros", "syn"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/syn"
-rust-version = "1.56"
+rust-version = "1.60"
 
 [features]
 default = ["derive", "parsing", "printing", "clone-impls", "proc-macro"]

README.md

@@ -46,7 +46,7 @@ contains some APIs that may be useful more generally.
 [`syn::DeriveInput`]: https://docs.rs/syn/2.0/syn/struct.DeriveInput.html
 [parser functions]: https://docs.rs/syn/2.0/syn/parse/index.html
 
-*Version requirement: Syn supports rustc 1.56 and up.*
+*Version requirement: Syn supports rustc 1.60 and up.*
 
 [*Release notes*](https://github.com/dtolnay/syn/releases)