fix(11895): remove duplicate networks in incoming transactions settin…

…gs (#12016)

## **Description**

We now list `mainnet` networks in the `rpcEndpoints` so the previous
logic rendering `mainnet` in separate functions are no longer need. Here
is the relevant
[PR](https://github.com/MetaMask/metamask-mobile/pull/11705/files) that
has those changes. The `rpcEndpoints` do not render in the right order
so filtering by Linea Mainnet and Ethereum Mainnet is needed.

## **Related issues**

Related Issue:
[#11895](#11895)

## **Manual testing steps**

1. Go to this settings page
2. Click on "Security & Privacy" 
3. Scroll down and toggle "Show incoming transactions" and confirm that
it works
4. Confirm that the duplicate `mainnet` networks are gone

## **Screenshots/Recordings**

![test](https://github.com/user-attachments/assets/b0bb2424-1b38-43fc-9953-69f5fec35242)

| Before | After
|:---:|:---:|
|![Simulator Screenshot - iPhone 16 Pro Max - 2024-10-24 at 13 37
34](https://github.com/user-attachments/assets/bdf394ca-fbda-449e-baa2-c9beed0cf5fb)|![incoming_transactions](https://github.com/user-attachments/assets/eaa4c27b-91e8-43d7-bb55-7860f6447e1e)|

### **Before**

NA

### **After**

NA

## **Pre-merge author checklist**

- [x] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.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
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [x] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [x] 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.