Revise description of localIdeographFontFamily example

[bdon]

Launch Checklist

The docs https://maplibre.org/maplibre-gl-js/docs/examples/local-ideographs/ state the opposite of what this setting actually does. Sped-up map load times with local ideographs is the default, and no setting is necessary, but setting it to false will disable local ideographs. Finally, setting the value only specifies device font fallbacks that override the style.

Related to #2990

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
• Add an entry to CHANGELOG.md under the ## main section.

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (249c830) 75.02% compared to head (994ece2) 75.02%.
Report is 4 commits behind head on main.

Additional details and impacted files

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  Hits        14346    14346           
  Misses       4776     4776           

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