[ic-select] Icon disappearing when disabled

### Summary of the bug

The icon in the `icon` slot disappears when the `disabled` prop is set to true.

### 🪜 How to reproduce

1. Open the ic-select storybook playground
2. Enable the ShowIcon control to show the icon
3. Set the select to be disabled
4. See that the Icon disappears

### 📸 Screenshots or code

_No response_

### 🖥 📱 Device

_No response_

### 🧐 Expected behaviour

The icon should remain and become greyed when the select is disabled.

### 📝 Acceptance Criteria

_No response_

### 🚨 Urgency (low, medium or high)

None

### Additional info

_No response_

Start with the ic-select Storybook playground and reproduce the issue using the ShowIcon control and disabled state. Trace the component implementation from that entry point, then verify that the icon remains visible and is greyed when disabled.

Written by the indexing model from the issue text.