stabilise fn_args_density configuration option

Author: scampi

Configurations.md

@@ -635,7 +635,7 @@ Argument density in functions
 
 - **Default value**: `"Tall"`
 - **Possible values**: `"Compressed"`, `"Tall"`, `"Vertical"`
-- **Stable**: No (tracking issue: #3375)
+- **Stable**: Yes
 
 #### `"Tall"` (default):
 

src/config/mod.rs

@@ -92,7 +92,7 @@ create_config! {
         the same line with the pattern of arms";
     force_multiline_blocks: bool, false, false,
         "Force multiline closure bodies and match arms to be wrapped in a block";
-    fn_args_density: Density, Density::Tall, false, "Argument density in functions";
+    fn_args_density: Density, Density::Tall, true, "Argument density in functions";
     brace_style: BraceStyle, BraceStyle::SameLineWhere, false, "Brace style for items";
     control_brace_style: ControlBraceStyle, ControlBraceStyle::AlwaysSameLine, false,
         "Brace style for control flow constructs";