fix: issue where mistakenly said EthTester can handle fork networks [APE-1392]

[antazoey]

What I did

it showed:

├── mainnet-fork
│   ├── foundry
│   ├── ganache
│   ├── hardhat
|   └── test (default)

even though that is not true.
so i realized someone (prolly me) mistakenly put the fork part in the providers instead of the networks but it was in both

How I did it

remove it from providers.
basically, copy all the other L2 plugins. this was the only one that was bad.

How to verify it

ape networks list --ecosystem polygon

all the fork networks should not have test as a provider.

Checklist

• Passes all linting checks (pre-commit and CI jobs)
• New test cases have been added and are passing
• Documentation has been updated
• PR title follows Conventional Commit standard (will be automatically included in the changelog)