skip validating S3 pre-signed POST length for CI flake

[bentsku]

Motivation

Follow up from #10314, I missed skipping the length in the ListObjectsV2 call, and this will most probably lead in CI failure as sometimes in CI the POST body is empty. We're still not quite sure what's happening here and it's not reproducible locally, but in the meantime we should avoid any CI blocks because of this.

Changes

• add the Size field in the snapshot ignore

[github-actions]

S3 Image Test Results (AMD64 / ARM64)

  2 files  ±0    2 suites  ±0   3m 24s ⏱️ +14s
389 tests ±0  338 ✅ ±0   51 💤 ±0  0 ❌ ±0 
778 runs  ±0  676 ✅ ±0  102 💤 ±0  0 ❌ ±0 

Results for commit 22be233. ± Comparison against base commit cc48a7c.

[coveralls]

coverage: 83.885% (-0.003%) from 83.888%
when pulling 22be233 on fix-presign-post-snapshot
into cc48a7c on master.

[github-actions]

LocalStack Community integration with Pro

    2 files  ±0      2 suites  ±0   1h 25m 10s ⏱️ -45s
2 660 tests ±0  2 409 ✅ ±0  251 💤 ±0  0 ❌ ±0 
2 662 runs  ±0  2 409 ✅ ±0  253 💤 ±0  0 ❌ ±0 

Results for commit 22be233. ± Comparison against base commit cc48a7c.

[macnev2013]

Just curious, are we only snapshot testing size parameter in this test case, or are there other tests where this is snapshot tested and works correctly?

It looks good to merge from my end!

[bentsku]

I think I'm going to wait a bit before merging until we actually hit the flake, maybe this is fixed now... 🤔 at least it's ready to merge at the first flake we see!

The issue seemed to happen only for S3 POST with form requests, they always work locally, but sometimes in CI, the file part of the form would just be empty, so the ETag and the size field would be different, but it would still be successful otherwise (not sure we can consider it a success though 🙃). Never could reproduce locally.

So let's see if we hit a flake and then I'll merge! Thanks for the review!