Site icon was not displayed in metamask mobile.

### **Description**
My site is written by vue.js, my site icon is correctly displayed in pc or mac, but only except metamask mobile,I don't know the reason,
I 'm very confused.

### **Technical Details**
This image below is my html head tag:
As you can see the red box on this image, there are three tags to set the icon of my site, they can work normally in pc or mac,but can't work in meta mobile.

my site icon is:

This image beblow is a screenshot of metamask mobile (page of Favorites):
Attention to the red box,my site icon can't displayed.

But the icon can work normally in metamask url bar:

So weird right?

### **Acceptance Criteria**
The MetaMask version of my iphone is v5.6.0 (950)

The icon can't displayed in "Favorites" page.

### **References**
I find it from myself,no reference, I can't find any correspond issue.

I wish someone who can help me,thank you!

The report names no repository file, test, or entry point; begin by reproducing the missing site icon in the MetaMask Mobile Favorites page and confirm the affected app version and platform. Done means determining whether the issue still occurs on a current version and documenting or fixing the Favorites icon behavior with a regression test.

Written by the indexing model from the issue text.