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/chain-selection/src/tree.rs

@@ -224,10 +224,11 @@ fn propagate_viability_update(
 				// finalized block is implicitly the viable leaf.
 				continue;
 			},
-			Some(entry) =>
+			Some(entry) => {
 				if entry.children.len() == pivot_count {
 					viable_leaves.insert(entry.leaf_entry());
-				},
+				}
+			},
 		}
 	}