Fix subscription icon

What does this MR do and why?

Subscription button mixed up subscription icons

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Go to any issue, for example http://gdk.test:3000/flightjs/Flight/-/issues/7
2. Click on subscription button

#474921 (closed)