fix: missing Oci-Subject header pushing index with subject

[jdolitsky]

This is an alternative to #1586 but missing the conformance test update

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Which issue does this PR fix:

What does this PR do / Why do we need it:

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Testing done on this change:

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Will this break upgrades or downgrades?

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #1589 (dff29e3) into main (41b05c6) will increase coverage by 0.02%.
The diff coverage is 72.72%.

❗ Current head dff29e3 differs from pull request most recent head 4f94a67. Consider uploading reports for the commit 4f94a67 to get more accurate results

@@            Coverage Diff             @@
##             main    #1589      +/-   ##
==========================================
+ Coverage   91.29%   91.32%   +0.02%     
==========================================
  Files         117      117              
  Lines       24293    24315      +22     
==========================================
+ Hits        22179    22206      +27     
+ Misses       1576     1568       -8     
- Partials      538      541       +3     

Impacted Files	Coverage Δ
pkg/storage/local/local.go	81.76% <72.72%> (-0.07%)	⬇️
pkg/storage/s3/s3.go	82.58% <72.72%> (-0.10%)	⬇️

... and 1 file with indirect coverage changes

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[andaaron]

The code changes that can be covered have been covered.

[rchincha]

lgtm