bug(gentest,rpc): `gentest` rpc error with `unexpected keyword argument 'extra_headers'`

On `main` 476f3c3e437:
```
uv run gentest 0x79510fa288a2d4d1bbe3794e3a079d2bcff0eb4550bc67e1ab6915b263979877 out2.py
```
fails with:
```
Traceback (most recent call last):
File "/home/dtopz/code/github/new/execution-spec-tests/.venv/bin/gentest", line 10, in
sys.exit(generate())
^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/.venv/lib/python3.12/site-packages/click/core.py", line 1442, in __call__
return self.main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/.venv/lib/python3.12/site-packages/click/core.py", line 1363, in main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/.venv/lib/python3.12/site-packages/click/core.py", line 1226, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/.venv/lib/python3.12/site-packages/click/core.py", line 794, in invoke
return callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/src/cli/gentest/cli.py", line 34, in generate
source = get_test_source(provider=provider, template_path="blockchain_test/transaction.py.j2")
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/src/cli/gentest/source_code_generator.py", line 47, in get_test_source
rendered_template = template.render(provider.get_context())
^^^^^^^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/src/cli/gentest/test_context_providers.py", line 97, in get_context
self._make_rpc_calls()
File "/home/dtopz/code/github/new/execution-spec-tests/src/cli/gentest/test_context_providers.py", line 48, in _make_rpc_calls
request = RPCRequest()
^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/src/cli/gentest/request_manager.py", line 37, in __init__
self.rpc = EthRPC(node_config.node_url, extra_headers=headers)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/dtopz/code/github/new/execution-spec-tests/src/ethereum_test_rpc/rpc.py", line 199, in __init__
super().__init__(*args, **kwargs)
TypeError: BaseRPC.__init__() got an unexpected keyword argument 'extra_headers'
```
```