Update all dependencies Docker tags

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
alpine	final	minor	3.12 -> 3.13
golang	stage	patch	1.15.6-alpine3.12 -> 1.15.7-alpine3.12

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Renovate configuration

📅 Schedule: "on the first day of the month" (UTC).

🚦 Automerge: Enabled.

♻️ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

👻 Immortal: This PR will be recreated if closed unmerged. Get config help if that's undesired.

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• If you want to rebase/retry this PR, check this box

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This PR has been generated by WhiteSource Renovate. View repository job log here.

[coveralls]

Pull Request Test Coverage Report for Build 526300727

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 79.268%

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Totals
Change from base Build 469040061:	0.0%
Covered Lines:	130
Relevant Lines:	164

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💛 - Coveralls