Not able to push changes after cleanup

[Harsimran1308]

I ran below command

java -jar bfg.jar --delete-files '*.pdf'
git reflog expire --expire=now --all && git gc --prune=now --agressive

The size is reduced at this point

When I do git push

It gives below error

remote : You are attempting to update refs that are reserved for Bitbucket's pull request functionality. Bitbucket manages these refs automatically, and they may not be updated by user.

remote: Rejected refs:
remote : refs/pull-request/206/ from
To [repo name]
![remote rejected] refs/pull-request/206/ from -> refs/pull-request/206/ from (pre-recive hook declined)