rustfmt: Drop util/atomic_counter.rs from exclusion list

Author: tnull

rustfmt_excluded_files

@@ -72,7 +72,6 @@ lightning/src/routing/router.rs
 lightning/src/routing/scoring.rs
 lightning/src/routing/test_utils.rs
 lightning/src/routing/utxo.rs
-lightning/src/util/atomic_counter.rs
 lightning/src/util/base32.rs
 lightning/src/util/byte_utils.rs
 lightning/src/util/config.rs