Update severity badge with new designs in the Vulnerability charts
### Background:
From this issue: https://gitlab.com/gitlab-org/gitlab/issues/34352 we are redesigning our severity badges to be more clear, quickly identifiable, scaleable, and accessible.
### Proposal:
| Current design | Proposed Design |
| ------ | ------ |
|  |  |
New badge designs:
| Old badge | New badge | New badge color |
| - | - | - |
|  |  | `#8B2615` |
|  |  | `#C0341D` |
|  |  | `#FCA429` |
|  |  | `#FDBC60` |
|  |  | `#418CD8` |
|  |  | `#919191` |
Text styling:
- Severity label text is always in GitLab's default paragraph style and color (unless defined otherwise)
- Severity label text is always sentence case (unless defined otherwise)
- Severity label text always has 8px padding between the icon and the severity text
Severity icon:
- Colors defined in table
- Icon is 12px x 12px
### Locations:
- Group security dashboard
- Instance security dashboard
issue