Align rustfmt edition settings

Author: lusingander

rustfmt.toml

@@ -17,7 +17,8 @@ short_array_element_width_threshold = 10
 match_arm_leading_pipes = "Never"
 fn_params_layout = "Tall"
 match_block_trailing_comma = false
-edition = "2015"
+edition = "2021"
+style_edition = "2021"
 merge_derives = true
 use_try_shorthand = false
 use_field_init_shorthand = false