Fix alpine plus dockerfile on alpine>=3.17

[Dean-Coakley]

Description of issue

alpine>=v3.17 upgrades openssl version v1.1.1w -> v3.0.x which brings a slight format change which broke key verification.

Openssl v1 format:

$ openssl rsa -pubin -in /tmp/nginx_signing.rsa.pub -text -noout
RSA Public-Key: (2048 bit)
Modulus:
    00:fe:14:f6:0a:1a:b8:86:19:fe:cd:ab:02:9f:58:
...

Openssl v3 format:

$ openssl rsa -pubin -in /tmp/nginx_signing.rsa.pub -text -noout
Public-Key: (2048 bit)
Modulus:
    00:fe:14:f6:0a:1a:b8:86:19:fe:cd:ab:02:9f:58:
...

Proposed changes

• Update expected key to match openssl=v3.0.x format
• Add sed replace to make old output format verify successfully against new key
• Add note so sed can be easily and safely removed in the future

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

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[codecov-commenter]

Codecov Report

Attention: 13 lines in your changes are missing coverage. Please review.

Comparison is base (a1b3635) 66.27% compared to head (e427b12) 66.25%.
Report is 3 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #511      +/-   ##
==========================================
- Coverage   66.27%   66.25%   -0.02%     
==========================================
  Files         118      118              
  Lines       13454    13457       +3     
==========================================
  Hits         8916     8916              
+ Misses       3944     3943       -1     
- Partials      594      598       +4     

Files	Coverage Δ
src/core/config/types.go	0.00% <ø> (ø)
src/core/config/defaults.go	13.63% <50.00%> (+13.63%)	⬆️
src/core/config/config.go	70.34% <33.33%> (+1.07%)	⬆️

... and 3 files with indirect coverage changes

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