Setting view command without icon renders label

[miguelsolorio]

Steps to Reproduce:

1. install pwa builder
2. go to the "store ready checklist view"
3. 🐛 hover over actions and see large label

You can see in the source code that no icon is set, causing the label to show. I think showing no action would be preferred.

      {
        "command": "pwa-studio.setWebURL",
        "title": "PWA Studio: Set App URL"
      },

[sandy081]

This is not specific to view container menu contribution and is true for all menu contributions. In case this has to be changed as requested, this has to fixed in menu registry where menu actions are populated as primary and secondary actions. Hence assigning it to @jrieken.