style: Migrate to stable-only rustfmt configuration

- Remove nightly-only features from .rustfmt.toml and vendor/ss58-registry/rustfmt.toml
- Removed features: imports_granularity, wrap_comments, comment_width,
  reorder_impl_items, spaces_around_ranges, binop_separator,
  match_arm_blocks, trailing_semicolon, trailing_comma
- Format all 898 affected files with stable rustfmt
- Ensures long-term reliability without nightly toolchain dependency

pezkuwi/node/core/backing/src/tests/mod.rs

@@ -51,8 +51,9 @@ struct TestLeaf {
 
 fn table_statement_to_primitive(statement: TableStatement) -> Statement {
 	match statement {
-		TableStatement::Seconded(committed_candidate_receipt) =>
-			Statement::Seconded(committed_candidate_receipt),
+		TableStatement::Seconded(committed_candidate_receipt) => {
+			Statement::Seconded(committed_candidate_receipt)
+		},
 		TableStatement::Valid(candidate_hash) => Statement::Valid(candidate_hash),
 	}
 }