.github: fix workflow format error

.github: fix workflow format error

    Warning: Encountered an error when evaluating display name ${{ format('python3 ceph/src/script/redmine-upkeep.py --github-action --git-dir=./ceph/ {0} {1}
    ', github.event_name == 'workflow_dispatch' && (inputs.debug && '--debug' || '') || '', github.event_name == 'workflow_dispatch' && format('--limit={}', inputs.limit) || '') }}. The template is not valid. .github/workflows/redmine-upkeep.yml (Line: 54, Col: 14): The following format string is invalid: --limit={}
    Error: The template is not valid. .github/workflows/redmine-upkeep.yml (Line: 54, Col: 14): The following format string is invalid: --limit={}

Signed-off-by: Patrick Donnelly <pdonnell@ibm.com>