Remove old group support for flexible general (#13514)

* Refactor card groups so splash is 3 and all others are not 3

* Support both grouping  versions for europe beta change over

* remove support for old group config which had splash at group 1

Author: abeddow91

dotcom-rendering/src/model/groupCards.ts

@@ -106,17 +106,11 @@ export const groupCards = (
 			};
 		}
 		case 'flexible/general': {
-			const hasv2Grouping = curated.some(
-				({ card }) => card.group === '3',
-			);
-			const splashGroup = hasv2Grouping ? '3' : '1';
-			const splash = curated.filter(
-				({ card }) => card.group === splashGroup,
-			);
+			const splash = curated.filter(({ card }) => card.group === '3');
 
 			// Backfilled cards will always be treated as 'standard' cards
 			const standard = [
-				...curated.filter(({ card }) => card.group !== splashGroup),
+				...curated.filter(({ card }) => card.group !== '3'),
 				...backfill,
 			];