runtime-rs: drop unused std::env import in initdata_block tests

The tests module imports std::env but never references it, which trips
the unused_imports warning during CI builds. Remove the dead import to
silence the warning.

Signed-off-by: Fabiano Fidêncio <ffidencio@nvidia.com>

src/runtime-rs/crates/resource/src/coco_data/initdata_block.rs

@@ -276,7 +276,6 @@ pub fn push_data(initdata_path: &Path, data: &str) -> anyhow::Result<()> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::env;
     use std::io::Read;
 
     #[test]