Prevent filling pending_block_operations table for RSK variant

[vbaranov]

Motivation

RSK chain doesn't have internal transactions. Thus, Blockscout needs to skip filling pending_block_operations table for RSK variant since there blocks with pending internal txs are stored there.

Changelog

Skip logic inside new_pending_operations for EthereumJSONRPC.RSK variannt.

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools

[coveralls]

Pull Request Test Coverage Report for Build 8bc488d4-0654-4771-bfd3-913c68b14be3

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 75.248%

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Totals
Change from base Build 1b033276-5d8e-4eb2-b64b-edbfe7748df8:	0.0%
Covered Lines:	5378
Relevant Lines:	7147

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💛 - Coveralls