This hack actually does the opposite now that we stopped using the miri script, so remove it

Author: oli-obk

ui_test/src/dependencies.rs

@@ -38,9 +38,6 @@ pub fn build_dependencies(config: &Config) -> Result<Dependencies> {
 
     // Reusable closure for setting up the environment both for artifact generation and `cargo_metadata`
     let setup_command = |cmd: &mut Command| {
-        // Avoid poisoning the target directory and causing unnecessary rebuilds.
-        cmd.env_remove("RUSTFLAGS");
-
         cmd.envs(envs.iter().map(|(k, v)| (k, v)));
         cmd.arg("--manifest-path").arg(manifest_path);
     };