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

bizinikiwi/primitives/npos-elections/src/pjr.rs

@@ -51,8 +51,8 @@ pub fn standard_threshold(
 ) -> Threshold {
 	weights
 		.into_iter()
-		.fold(Threshold::zero(), |acc, elem| acc.saturating_add(elem)) /
-		committee_size.max(1) as Threshold
+		.fold(Threshold::zero(), |acc, elem| acc.saturating_add(elem))
+		/ committee_size.max(1) as Threshold
 }
 
 /// Check a solution to be PJR.