Docs: ~= is missing as valid specifier

[BastianZim]

According to the docs ~= is not supported as a specifier but it seems to have been introduced in https://github.com/conda/conda-build/releases/tag/3.20.5

Note: This came up in conda/grayskull#348

[github-actions]

Hi there, thank you for your contribution!

This issue has been automatically marked as stale because it has not had recent activity. It will be closed automatically if no further activity occurs.

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Thanks!

[BastianZim]

Still an issue

[ryanskeith]

I can work this.