Change Solc binary downloader path to official primary supported path

[vbaranov]

Motivation

https://ethereum.github.io/solc-bin/bin/soljson-#{version}.js URL to download Solc binary doesn't work for the version of compiler >= 0.7.2

Changelog

Change Solc compiler download URL to https://solc-bin.ethereum.org/bin/soljson-#{version}.js. It is officially supported primary way https://gitter.im/ethereum/solidity-dev?at=5f8418f402e81701b017f522.

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 d81e6630fdf58b855b36bd884ab176df1b722df3-PR-3341

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+3.6%) to 74.727%

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Files with Coverage Reduction	New Missed Lines	%
lib/block_scout_web/controllers/chain/market_history_chart_controller.ex	1	78.57%

Totals
Change from base Build 9b7438f3c1a726913610b94d37b7ac1acc8245c3:	3.6%
Covered Lines:	1987
Relevant Lines:	2659

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💛 - Coveralls