Elixir upgrade to 11.2

[vbaranov]

Motivation

Upgrade Elixir version

Changelog

• Update Elixir, Erlang versions in GA CI
• Update .tool-versions
• Update bitwalker/alpine-elixir-phoenix to the latest tag

Chore:

• Update spandex libraries

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 4206e477aed3b9f4d5156d08f2bf08712e18f8ef-PR-3484

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.8%) to 66.969%

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Files with Coverage Reduction	New Missed Lines	%
lib/block_scout_web/channels/address_channel.ex	2	36.96%
lib/block_scout_web/controllers/chain/market_history_chart_controller.ex	2	71.43%
lib/block_scout_web/notifier.ex	2	82.76%

Totals
Change from base Build 8b4d31d3426a1467b6c557490cd638227f647644:	0.8%
Covered Lines:	2066
Relevant Lines:	3085

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💛 - Coveralls