Remove sizes attribute when responsive images are disabled

[mukeshpanchal27]

Summary

Fixes #1389

Check the issue description for testing details.

[mukeshpanchal27]

As WordPress core does not add sizes attribute for thumbnail size, In e83ac2d i have to remove it from tests.

Is there any specific reason for it 🤔

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>
Co-authored-by: adamsilverstein <adamsilverstein@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[adamsilverstein]

As WordPress core does not add sizes attribute for thumbnail size, In e83ac2d i have to remove it from tests.

were tests failing without this change?

Is there any specific reason for it 🤔

I was wondering as well. Maybe for HDPI versions of thumbnails (x2) if that were a thing? For picture element we want srcset for fallbacks, but not sure why we would want sizes.

[adamsilverstein]

Nice!

[mukeshpanchal27]

@westonruter @adamsilverstein or @swissspidy Could you please review and merge it. Thanks!