Update alpine-elixir-phoenix 1.11.3

[vbaranov]

Motivation

Run Docker setup on Elixir 1.11.3

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 64eb65ddff352e78ea7f2c716cc3322bafa245b3-PR-3717

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.5%) to 64.424%

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Files with Coverage Reduction	New Missed Lines	%
lib/block_scout_web/checksum_address.ex	6	55.56%

Totals
Change from base Build 38f1665db93f412c7be51fd36f8589d833db4321:	0.5%
Covered Lines:	2097
Relevant Lines:	3255

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💛 - Coveralls