**Describe the bug** Unable to access clear button on `EuiComboBox` from keyboard navigation.  1. Go to https://eui.elastic.co/#/forms/combo-box 2. Click to focus and open any clearable `comboBox` 3. Make a selection so the input is filled 4. Press <kbd>esc</kbd> to close list and <kbd>tab</kbd> to the `x` clear button 5. Press <kbd>enter</kbd> to clear the selection 6. Notice nothing happens Clicking the `x` has the intended affect just not via keyboard interaction.