Minor bugfix in `metadata-push`.

Third time's the charm... Followup from:
!18 (merged) + !19 (merged)

https://gitlab.cern.ch/lhcb/tck-specs/-/jobs/39222781

create mode 100644 ann/json/eb/eb1d504b.json
$ PUSH_CMD="git push origin/master"
$ if [ "$CI_COMMIT_BRANCH" = 'main' ] && [ $(cat ../../isDev.txt) = 'false' ]; then eval $PUSH_CMD; else echo "DRY_RUN thus skipping $PUSH_CMD"; fi
fatal: 'origin/master' does not appear to be a git repository
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.