Consistently quote TOML strings

Author: Maroloccio

Configurations.md

@@ -1784,8 +1784,8 @@ See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
 
 Controls whether to include a leading pipe on match arms
 
-- **Default value**: `Never`
-- **Possible values**: `Always`, `Never`, `Preserve`
+- **Default value**: `"Never"`
+- **Possible values**: `"Always"`, `"Never"`, `"Preserve"`
 - **Stable**: Yes
 
 #### `Never` (default):