chore(deps): update bitwalker/alpine-elixir-phoenix docker tag to v1.15.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
bitwalker/alpine-elixir-phoenix	final	minor	1.14.0 -> 1.15.0
bitwalker/alpine-elixir-phoenix	stage	minor	1.14.0 -> 1.15.0

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Configuration

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[coveralls]

Pull Request Test Coverage Report for Build 9add485bb2caf26edd82a5b2419ac7ed191976d4-PR-1480

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 54.953%

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Totals
Change from base Build d315fac2ff1ba99e3571ed82d315e8670cd582e7:	-0.02%
Covered Lines:	3301
Relevant Lines:	6007

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💛 - Coveralls