Forbid unsafe code (#1704)

We can reverse this later if it really becomes necessary, but I expect
safe Rust to be sufficient for all our needs.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

ruff_dev/src/lib.rs

@@ -10,6 +10,7 @@
     clippy::similar_names,
     clippy::too_many_lines
 )]
+#![forbid(unsafe_code)]
 
 pub mod generate_all;
 pub mod generate_cli_help;

ruff_dev/src/main.rs

@@ -10,6 +10,7 @@
     clippy::similar_names,
     clippy::too_many_lines
 )]
+#![forbid(unsafe_code)]
 
 use anyhow::Result;
 use clap::{Parser, Subcommand};