Update docker.io/library/postgres Docker tag to v15 - autoclosed

[renovate]

This PR contains the following updates:

Package	Update	Change
docker.io/library/postgres	major	9.6 -> 15.4

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Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

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

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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

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[coveralls]

Pull Request Test Coverage Report for Build 5837404882

• 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 90.077%

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Totals
Change from base Build 5749134370:	0.0%
Covered Lines:	4430
Relevant Lines:	4918

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💛 - Coveralls

[codecov]

Codecov Report

Merging #56 (8c0008f) into master (50a7f09) will decrease coverage by 0.06%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

❗ Current head 8c0008f differs from pull request most recent head ec27833. Consider uploading reports for the commit ec27833 to get more accurate results

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
- Coverage   90.13%   90.07%   -0.06%     
==========================================
  Files          52       53       +1     
  Lines        4816     4918     +102     
==========================================
+ Hits         4341     4430      +89     
- Misses        475      488      +13     

see 3 files with indirect coverage changes