Fix e2e testing for mock frame data in `inbox`

[nuke-web3]

OK. Ran unit tests and seeing a failure which seems to be unrelated to blobs, but other blob tests look good:

=== RUN   TestIndexer_E2E_CalldataAndCelestia
    harness_test.go:160: [hint] calldata tx included in L1 block 703 (0xa2e657240289a5900eb34b1be2e33f570d7016714993474ae82713b247f766c4)
    harness_test.go:164: [hint] submitted celestia blob at height=9290241 namespace=0000000000000000000000000000000000000001010101010101010101 commitment=2b783b93b670df59c7b4fae8fda05e3b88a906bd99c5bec40d6129f12c809a32
    harness_test.go:168: [hint] alt-da commitment tx included in L1 block 706 (0xad8e5c8b3252dd2d3e9a89a755bc36df989796fe99289b8003b1c599cf655e00)
    harness_test.go:171: indexer did not store any locations in time.
        Current store status: indexed_blocks=0 last_indexed_block=716
        Hints:
        - Ensure geth is producing blocks (mining/automine).
        - Ensure the batch inbox address matches the tx 'to' address: 0x8943545177806ED17B9F23F0a21ee5948eCaa776
        - Check indexer logs for batch/frame decode errors.

Would revert the readme change of response type back to "ethereum", as we're differentiating blobs based on other fields now.

Originally posted by @tuxcanfly in #530 (review)

[nuke-web3]

celestiaorg/op-da-indexer#1