Replace deprecated rustfmt.toml options (payjoin#687)

Using the nightly toolchain the `version` and `hide_parse_errors` options
are now deprecated:

[version](https://rust-lang.github.io/rustfmt/?version=v1.8.0&search=#version)

[hide_parse_errors](https://rust-lang.github.io/rustfmt/?version=v1.8.0&search=#hide_parse_errors)

Author: DanGould

rustfmt.toml

@@ -59,7 +59,7 @@ match_block_trailing_comma = false
 blank_lines_upper_bound = 1
 blank_lines_lower_bound = 0
 edition = "2018"
-version = "One"
+style_edition = "2018"
 inline_attribute_width = 0
 format_generated_files = true
 merge_derives = true
@@ -71,7 +71,7 @@ color = "Auto"
 unstable_features = false
 disable_all_formatting = false
 skip_children = false
-hide_parse_errors = false
+show_parse_errors = true
 error_on_line_overflow = false
 error_on_unformatted = false
 emit_mode = "Files"