BOOKKEEPER-939: Fix typo of bookkeeper merge pr script

There is typo of bk-merge-pr.py script on merging pr without a jira id.

Author: Sijie Guo <sijie@apache.org>

Reviewers: Matteo Merli <mmerli@apache.org>

Closes #53 from sijie/sijie/fix_merge_script
1 file changed