Remove duplicate nodeName field from indexing

[abjerner]

Removed duplicate 'nodeName' field from index values.

📋 Description

The UmbracoExamineFieldNames.NodeNameFieldName constant equals to nodeName, so no reason to add the same field twice.

As the example uses the indexer property of the dictionary, this doesn't actually cause any errors, but I thought I might as well fix it.

As I'm removing code, I haven't checked any of the boxes in the checkbox below.

📎 Related Issues (if applicable)

✅ Contributor Checklist

I've followed the Umbraco Documentation Style Guide and can confirm that:

• Code blocks are correctly formatted.
• Sentences are short and clear (preferably under 25 words).
• Passive voice and first-person language (“we”, “I”) are avoided.
• Relevant pages are linked.
• All links work and point to the correct resources.
• Screenshots or diagrams are included if useful.
• Any code examples or instructions have been tested.
• Typos, broken links, and broken images are fixed.

Product & Version (if relevant)

Deadline (if relevant)

📚 Helpful Resources

• 🧾 Umbraco Contribution Guidelines
• ✍️ Umbraco Documentation Style Guide

[eshanrnh]

Thanks for fixing the code, @abjerner 🙌