UI Feature Config: Matrix-iOS does not appear to honor the UIFeature.voip setting in element-config.json, call buttons show even when set to false.

### Steps to reproduce

1. On an Element server, edit element-config.json and add the following:
"setting_defaults": {
"UIFeature.voip": false,
}
2. Sign into that server using Element-iOS.
3. Open a room / 1:1 conversation and check for the Video and Audio Call buttons.

### Outcome

#### What did you expect?
The buttons to start a call should no longer be present with UIFeature.voip set to false.
#### What happened instead?
Call buttons are still visible in the UI and can still be used to initiate a call.

### Your phone model

iPhone 13 Pro

### Operating system version

iOS 15.6

### Application version

Element v1.8.22 (22020713143628)

### Homeserver

matrix.bvipilots.net

### Will you send logs?

No

Start by tracing how the UIFeature.voip value from element-config.json is read in Element-iOS and how it controls the Video and Audio Call buttons. Reproduce with UIFeature.voip set to false, then verify that both buttons are absent and cannot initiate a call.

Written by the indexing model from the issue text.