Reformat imports to a consistent style for imports

rustfmt.toml configuration:
  imports_granularity = "One"
  group_imports = "One"

runtime/src/commitment.rs

@@ -1,6 +1,8 @@
-use solana_sdk::{clock::Slot, commitment_config::CommitmentLevel};
-use solana_vote_program::vote_state::MAX_LOCKOUT_HISTORY;
-use std::collections::HashMap;
+use {
+    solana_sdk::{clock::Slot, commitment_config::CommitmentLevel},
+    solana_vote_program::vote_state::MAX_LOCKOUT_HISTORY,
+    std::collections::HashMap,
+};
 
 pub const VOTE_THRESHOLD_SIZE: f64 = 2f64 / 3f64;