[DOCS] Refine the Waligora pine description in the spatial stats post

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• No: this is a documentation update. The PR name follows the format [DOCS] my subject

What changes were proposed in this PR?

Small follow-up to the spatial statistics blog post (#3219):

• Correct the description of the Sosna Waligora pine: its claim to fame is girth (long billed as Poland's thickest pine, near Sulechow), not isolation — it merely stands alone, which is why LOF flags it. Reworded for accuracy (and a little fun).
• Remove Polish typographic quotes from prose and the figure annotation (they remain in the raw output table, which shows the actual data).
• Note the sample dataset's provenance: the bundled Lubusz POI shapefile is PMC member Pawel's hometown region.

How was this patch tested?

• Rebuilt the LOF figure from the same exported results (annotation text only; data unchanged); PNG re-optimized with the oxipng manual-stage hook (verified idempotent pass).
• pre-commit passes on the changed files; post re-verified in a local mkdocs build.

Did this PR include necessary documentation updates?

• Yes, I have updated the documentation.