Bump MSRV to 1.60

This is the minimum of once_cell 1.18.0 (selected via ring ->
web-sys -> wasm-bindgen -> wasm-bindgen-macro -> wasm-bindgen-macro-support ->
wasm-bindgen-backend -> once_cell).

.github/workflows/ci.yml

@@ -92,11 +92,8 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@master
         with:
-          # MSRV: Rust 1.47 and later have bugs in rustc that prevent some
-          # projects from upgrading past 1.46 yet. So, maintain compatibility
-          # for 1.46 until those bugs are fixed.
           # Make sure to update rust-version in Cargo.toml when updating MSRV.
-          toolchain: 1.46.0
+          toolchain: "1.60"
 
       - run: |
           cargo check --lib --all-features

Cargo.toml

@@ -16,7 +16,7 @@
 categories = ["cryptography", "no-std"]
 description = "Web PKI X.509 Certificate Verification."
 edition = "2018"
-rust-version = "1.46"
+rust-version = "1.60"
 license-file = "LICENSE"
 name = "rustls-webpki"
 readme = "README.md"