Use dedicated Faviconkit subdomain (`metamask.faviconkit.com`)

### **Description**

Hi there! We’re super proud to be MetaMask’s choice for serving favicons! To ensure continuous uptime, we’ve given the project its own dedicated subdomain, `metamask.faviconkit.com`.

### **Technical Details**

- Get icons from `https://metamask.faviconkit.com` instead of ~~`https://api.faviconkit.com`~~
- Replace all occurences of ~~`https://api.faviconkit.com`~~ with `https://metamask.faviconkit.com`

### **Acceptance Criteria**

- Web site favicons load from `https://metamask.faviconkit.com`

### **References**

- none

No file or test is named. Search the repository for `https://api.faviconkit.com`, inspect each favicon-loading entry point, and replace the endpoint with `https://metamask.faviconkit.com`. Verify that website favicons load successfully from the dedicated subdomain.

Written by the indexing model from the issue text.