ci: use Rust 1.53.0 for lints

Clippy panics for this codebase on 1.54.0. See rust-lang/rust-clippy#7523.

Author: arxanas

.github/workflows/lint.yml

@@ -15,7 +15,9 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          # Clippy panics on 1.54.0, see
+          # https://github.com/rust-lang/rust-clippy/issues/7523
+          toolchain: 1.53.0
           components: rustfmt, clippy
       - name: Run `cargo fmt`
         uses: actions-rs/cargo@v1