docs: match the region Source option labels to the UI casing

Author: igorlukanin

docs-mintlify/docs/explore-analyze/charts/chart-types/map.mdx

@@ -58,7 +58,7 @@ Clustering groups nearby points into a single circle that expands on zoom. It is
 
 A region map requires:
 
-- **Source** — the GeoJSON to render: `World countries`, `US states`, or `Custom`.
+- **Source** — the GeoJSON to render: `World Countries`, `US States`, or `Custom`.
 - **Property** — which property in each GeoJSON feature acts as the join key (e.g. `name`, `ISO3166-1-Alpha-2`, `ISO3166-1-Alpha-3`, `state_code`).
 - **Dimension** — which column from your query joins to **Property**.
 - **Measure** — the numeric measure that drives the choropleth fill.
@@ -71,11 +71,11 @@ The choropleth gradient comes from the active palette — pick from the built-in
 
 ### Country name matching
 
-With **World countries**, country names do not have to be spelled the way the boundary data spells them. Long forms, endonyms, and common abbreviations all resolve to the same country, so `United States`, `United States of America`, and `USA` are interchangeable, as are `Brasil` and `Brazil`, or `Deutschland` and `Germany`. The same applies to the 2- and 3-letter ISO code properties, and it works in either direction — a name in your data still matches when **Property** is set to a code.
+With **World Countries**, country names do not have to be spelled the way the boundary data spells them. Long forms, endonyms, and common abbreviations all resolve to the same country, so `United States`, `United States of America`, and `USA` are interchangeable, as are `Brasil` and `Brazil`, or `Deutschland` and `Germany`. The same applies to the 2- and 3-letter ISO code properties, and it works in either direction — a name in your data still matches when **Property** is set to a code.
 
 Matching is exact, never approximate: `United States` resolves to the United States and never to `United States Minor Outlying Islands`. Bare 2-letter codes such as `US` are only treated as country codes when **Property** is set to one of the ISO code properties, so a column of US state codes joined against country names stays unmatched rather than coloring `DE` as Germany.
 
-This applies to **World countries** only. With **US states** or **Custom**, values must match the chosen **Property** exactly (ignoring case and surrounding whitespace).
+This applies to **World Countries** only. With **US States** or **Custom**, values must match the chosen **Property** exactly (ignoring case and surrounding whitespace).
 
 ### Custom GeoJSON