cbindgen tests are failing with whitespace changes

See e.g. https://gitlab.torproject.org/legoktm/arti/-/jobs/632650

$ ./maint/cbindgen --check
arti-rpc-client-core ...
--- arti-rpc-client-core.h	2024-08-10 19:50:21.143386980 +0000
+++ arti-rpc-client-core.h.tmp	2024-08-10 20:40:59.307498410 +0000
@@ -432,7 +432,7 @@
 void arti_rpc_err_free(ArtiRpcError *err);
 
 #ifdef __cplusplus
-} // extern "C"
-#endif // __cplusplus
+}  // extern "C"
+#endif  // __cplusplus
 
-#endif /* ARTI_RPC_CLIENT_CORE_H_ */
+#endif  /* ARTI_RPC_CLIENT_CORE_H_ */
  (No changes in the warnings)
------------------------------
At least one file changed; see above for diffs.
(Running in 'check' mode, so nothing was changed.)

If I had to guess, it's probably because of the new cbindgen release (see https://github.com/mozilla/cbindgen/blob/v0.27.0/CHANGES)