fix exchange rate websocket update for Rootstock

[ayrat555]

Rootstock has custom logic for market cap calculation that
uses data from DB. This PR add required feilds to exchange_rate
when sending it through a web socket.

Changelog

• fix exchange rate WebSocket update for Rootstock

[coveralls]

Pull Request Test Coverage Report for Build fb298a58-440f-42d7-8f8e-2dcd68c441e6

• 2 of 3 (66.67%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.06%) to 78.472%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/block_scout_web/lib/block_scout_web/notifier.ex	2	3	66.67%

Files with Coverage Reduction	New Missed Lines	%
apps/block_scout_web/lib/block_scout_web/controllers/chain/market_history_chart_controller.ex	2	71.43%

Totals
Change from base Build a1315136-be1b-4c82-84db-4ee7956e3d0f:	0.06%
Covered Lines:	5187
Relevant Lines:	6610

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💛 - Coveralls