minor polish code

Author: zjregee

datafusion/functions/benches/uuid.rs

@@ -24,7 +24,6 @@ use datafusion_functions::string;
 
 fn criterion_benchmark(c: &mut Criterion) {
     let uuid = string::uuid();
-
     c.bench_function("uuid", |b| {
         b.iter(|| {
             black_box(uuid.invoke_with_args(ScalarFunctionArgs {

datafusion/functions/src/string/concat_ws.rs

@@ -402,7 +402,6 @@ fn is_null(expr: &Expr) -> bool {
 #[cfg(test)]
 mod tests {
     use std::sync::Arc;
-    use std::vec;
 
     use arrow::array::{Array, ArrayRef, StringArray};
     use arrow::datatypes::DataType::Utf8;