rustfmt: Drop lightning-invoice/tests/ser_de.rs from exclusion list

Author: tnull

rustfmt_excluded_files

@@ -1,7 +1,6 @@
 lightning-invoice/fuzz/fuzz_targets/serde_data_part.rs
 lightning-invoice/src/payment.rs
 lightning-invoice/src/utils.rs
-lightning-invoice/tests/ser_de.rs
 lightning/src/blinded_path/message.rs
 lightning/src/blinded_path/mod.rs
 lightning/src/blinded_path/payment.rs