Fix missing Change-Id

The pull request 43a311d mistakenly set the trailers_by variable to
DEFAULT_TRAILERS_BY, causing the change ID to disappear. Change
the variable to KNOWN_TRAILERS_BY to ensure the change ID appears
correctly.

Co-authored-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Change-Id: I4e3b4bfa06aba31bed2c26925ecfa5593a3d327b

Author: charliechiou

scripts/commit-msg.hook

@@ -186,7 +186,7 @@ build_commit_trailer_regex() {
   done < <(git config --get-regexp 'trailer.*.key')
 
   if [[ ${#trailers_by[@]} -eq 0 ]]; then
-    trailers_by=("${DEFAULT_TRAILERS_BY[@]}")
+    trailers_by=("${KNOWN_TRAILERS_BY[@]}")
   fi
 
   # Possible trailers :