refactor: remove training property description, add svgIconURL, drop old migration and create new

- since app was not deployed yet, i deleted the migration to keep them clean

lib/content/training.ts

@@ -7,11 +7,11 @@ type Training = {
     id: string;
     name: string;
     slug: string;
-    description: string;
     days: number;
     weight: number;
     draft?: boolean;
     logoURL?: string;
+    svgIconURL?: string;
     repositoryURL?: string;
     priceOpen: number;
     priceCorporate: number;