Custom network is not reset when a wallet is restored

[srirambv]

Description

Custom network is lost when wallet is restored

Steps to Reproduce

1. Create a new wallet account
2. Add a custom network manually or via https://chainlist.org
3. Set network to custom network added in step 2
4. Check brave://settings/wallet/networks/ to see the custom network added
5. Restore a different wallet using back seed words
6. Network dropdown is empty doesn't default to Mainnet
7. Check settings, custom network is removed as expected

Actual result:

Custom.network.mov

Expected result:

Network setting should reset to default (Mainnet) for the new wallet

Reproduces how often:

Easy

Brave version (brave://version info)

Brave	1.33.83 Chromium: 96.0.4664.45 (Official Build) beta (arm64)
Revision	76e4c1bb2ab4671b8beba3444e61c0f17584b2fc-refs/branch-heads/4664@{#947}
OS	All

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• Can you reproduce this issue with the beta channel? Yes
• Can you reproduce this issue with the nightly channel? Yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? NA
• Does the issue resolve itself when disabling Brave Rewards? NA
• Is the issue reproducible on the latest version of Chrome? NA

Miscellaneous Information:

cc: @bbondy @darkdh

[srirambv]

Brave	1.36.90 Chromium: 98.0.4758.87 (Official Build) beta (64-bit)
Revision	e4cd00f135fb4d8edc64c8aa6ecbe7cc79ebb3b2-refs/branch-heads/4758@{#1002}
OS	☑️ Linux	☑️ Windows 11 Version Dev (Build 22523.1000)	☑️ macOS Version 12.0.1 (Build 21C52)
Verified steps from issue description Verified adding a custom network and setting as default and restoring a new seed word retains the custom network