rustfmt: Drop lightning-custom-message/src/lib.rs from excluded

.. files

Author: tnull

rustfmt_excluded_files

@@ -1,6 +1,5 @@
 ./bench/benches/bench.rs
 ./lightning-background-processor/src/lib.rs
-./lightning-custom-message/src/lib.rs
 ./lightning-invoice/fuzz/fuzz_targets/serde_data_part.rs
 ./lightning-invoice/src/de.rs
 ./lightning-invoice/src/lib.rs