Fix undeclare button not showing an icon

Using:
Nuxeo Web UI 3.0.29
nuxeo-retention-2021.6.6

Create a retention rule:

• Allow undeclaring record: yes
• Immediate start
• Duration 1 day

Create a File
Attach the retention rule on the File document
=> Document goes under retention

Open document actions menu
=> Undeclare record option is shown without an icon (bug)
Expected: icon should be visible