Reduce duplication of Popular networks within e2e

### What is this about?

This task aims to reduce duplication by using the CustomNetworks.tsx list instead of duplicating it in networks.e2e.js. To achieve this, we need to update the network state in the fixture builder class to align with the CustomNetworks list.

### Scenario

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### Design

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### Technical Details

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### Threat Modeling Framework

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### Acceptance Criteria

All networks related e2e should pass

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

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Compare the Popular networks list in CustomNetworks.tsx with networks.e2e.js, then inspect the fixture builder class that provides network state. Align the fixture state with CustomNetworks.tsx and run all network-related e2e tests; done means those tests pass without a duplicated network list.

Written by the indexing model from the issue text.