Fixing the iterator of SemistandardMultiSkewTableaux

[tscrim]

Fixes #36196 as the iterator does not update the position as it goes through the word.

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[tscrim]

@ghseeli Here is a fix; it was a simple bug.

[github-actions]

Documentation preview for this PR (built with commit eed72b2; changes) is ready! 🎉

[ghseeli]

@ghseeli Here is a fix; it was a simple bug.

@tscrim Thank you! I am glad some fixes can be simple :-)

[tscrim]

@ghseeli Should I interpret that as a positive review? (Due to the new GH process, you can't "officially" set a positive review, which makes the review process much more controlled (to put it very nicely).)

[fchapoton]

good

[tscrim]

Thank you.