Remove unused function in results.py

[seanpwlms]

It looks like _get_or_create_default_storage is not invoked anywhere, so this PR removes it.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

[cicdw]

I love a good cleanup - thank you @seanpwlms !

[codspeed-hq]

CodSpeed Performance Report

Merging #14744 will not alter performance

_{Comparing remove_unused_function (b7b5eae) with main (e2832e2)}

Summary

✅ 5 untouched benchmarks