Remove colors for Add and Import buttons

### Plugin version

v0.3.0

### NetBox version

v4.3.2

### Feature type

Change to existing functionality

### Proposed functionality

Remove the colors from the Add and Import buttons to match the changes in Netbox 4.3.

### Use case

Unified GUI with the rest of Netbox 4.3

### Database changes

_No response_

### External dependencies

_No response_