fix: fix network delete trash displayed on mouse over (#25547)

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## **Description**
the delete network trash logo should be displayed only when we have
mouse over
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also include relevant motivation and context. Have in mind the following
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1. What is the reason for the change?
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## **Related issues**

Fixes:

## **Manual testing steps**

1. Add any popular network
2. Go to network modal
3. check if the trash icon is displayed without mouse over

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**

<!-- [screenshots/recordings] -->


https://github.com/MetaMask/metamask-extension/assets/26223211/b720aff8-54b7-4430-b267-4d3ed39a67e2


### **After**

<!-- [screenshots/recordings] -->


https://github.com/MetaMask/metamask-extension/assets/26223211/dd8783ee-a6a8-4a37-96c1-665d5a5a7ccb



## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
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if applicable
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guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

ui/components/multichain/network-list-item/index.scss

@@ -14,6 +14,14 @@
     color: inherit;
   }
 
+  &:hover,
+  &:focus,
+  &:focus-within {
+    .multichain-network-list-item__delete {
+      visibility: visible;
+    }
+  }
+
   &__network-name {
     width: 100%;
     flex: 1;
@@ -36,4 +44,8 @@
     top: 4px;
     left: 4px;
   }
+
+  &__delete {
+    visibility: hidden;
+  }
 }