use 'key' in dict rather than dict.get('key') for JS compatibility

This fails in JS because `properties` is a JS object, not a dict, and JS objects don't have 'get'.
We get around this by using `in`. It's not as elegant but it's foolproof

src/emcommon/metrics/footprint/util.py

@@ -101,10 +101,10 @@ async def get_egrid_region(coords: list[float, float], year: int) -> str | None:
         return None
     region_feature = get_feature_containing_point(coords, geojson)
     if region_feature is not None:
-        properties = region_feature['properties']
-        region_name = properties.get('name') or properties.get('SUBRGN')
-        if region_name:
-            return region_name
+        if 'name' in region_feature['properties']:
+            return region_feature['properties']['name']
+        if 'SUBRGN' in region_feature['properties']:
+            return region_feature['properties']['SUBRGN']
     Log.warn(f"An eGRID region was not found for coords {coords} in year {year}.")
     return None