fix(kms): remove dead import of removed KmsClient in local_export tests

The test module in local_export.rs imported crate::backends::KmsClient,
which was removed in commit 76b3c085b (refactor(kms): fold the KmsClient
layer into KmsBackend). This caused a compile error in the clippy-check
step. Remove the dead import; LocalKmsClient is already available via
use super::*.

crates/kms/src/backup/local_export.rs

@@ -560,7 +560,6 @@ async fn fsync_dir(path: &Path) -> Result<()> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::backends::KmsClient;
     use crate::config::LocalConfig;
     use std::sync::Arc;
     use tempfile::TempDir;