docs: fix typo of sibling

[motss]

Description

The docs is showing siblings for the sibling value which should be sibling without s.

Additional context

None

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.
• Read contribution guidelines.

[azat-io]

Thank you!