Create a New Page - Modal : Combobox is missing appropriate roles and/or attributes

Issue Summary

On "Create a Space" modal dialog, the combo-box for "Select a space" element (which becomes available when user activates "Create" link from header region) is coded inappropriately. 

Steps to Reproduce

1. Navigate to "Create" link present in header region and activate it.
2. Navigate to "Select a space" element and activate it with Space bar key.
3. Observe that "Select a space" element functions like combo-box.

Actual Behaviour

The "Select a space" element is missing roles and attributes due to which screen reader users not able to interact with it effectively.

Expected Behaviour

The "Select a space" element should be coded with role="combo-box" effectively. When user navigates to the items/options for "Suggested Spaces" and "All spaces" with up/down keys it should convey by screen reader.

For more information on accessible combo-boxes please follow this link -> https://www.w3.org/TR/wai-aria-practices-1.1/examples/combobox/aria1.1pattern/listbox-combo.html 

Screenshot

Workaround

workaround

Bug Ref: 723879