[ic-button] Icon variant reads label twice to Voiceover screenreader

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### Summary of the bug
Using Voiceover, icon button variants read their label out twice.
This occurs in Icon Buttons, and the close button in Dialog and the incoming Drawer (because they're both icon buttons).

This issue doesn't seem to occur on NVDA. Somehow VO is reading the tooltip text (if disableTooltip is true, the label only reads once) and NVDA isn't.

### 🪜 How to reproduce
Tell us the steps to reproduce the problem:
1. Go to [Button - Icon only](https://mi6.github.io/ic-ui-kit/branches/develop/react/?path=/story/button--icon-only) story
2. Turn on Voiceover and tab through the buttons
3. Notice that the label of the button is read twice.

### 📸 Screenshots or code

### 🖥 📱 Device
- Type: Desktop
- Device: Macbook
- Browser version: Chrome

### 🧐 Expected behaviour
Would expect it only to read the button label once.

Whatever the solution is, it mustn't negatively impact behaviour in NVDA.

### 🚨 Urgency (low, medium or high)
If applicable, tell us how urgent it is that this issue gets resolved, based on the impact it has on your team's work or project timeline.

Low

Use the linked Button - Icon only story as the reproduction entry point. Trace the icon-button tooltip and label behavior, including the Dialog close button and incoming Drawer cases, while comparing VoiceOver with NVDA. Done means VoiceOver reads the label once and NVDA behavior remains unchanged.

Written by the indexing model from the issue text.