rustfmt: Use fn_params_layout

The option `fn_args_layout` has been deprecated in favour of
`fn_params_layout`.

Author: tcharding

rustfmt.toml

@@ -50,7 +50,7 @@ enum_discrim_align_threshold = 0
 match_arm_blocks = false        # Default true
 match_arm_leading_pipes = "Never"
 force_multiline_blocks = false
-fn_args_layout = "Tall"
+fn_params_layout = "Tall"
 brace_style = "SameLineWhere"
 control_brace_style = "AlwaysSameLine"
 trailing_semicolon = true