Update alter_foreign_key.go rm redundant comment

Author: elianddb

sql/plan/alter_foreign_key.go

@@ -651,13 +651,8 @@ func foreignKeyComparableTypes(ctx *sql.Context, type1 sql.Type, type2 sql.Type)
 	t1 := type1.Type()
 	t2 := type2.Type()
 
-	// Handle time-related types with different precisions or cross-type references
+	// MySQL allows time-related types to reference each other in foreign keys:
 	if (types.IsTime(type1) || types.IsTimespan(type1)) && (types.IsTime(type2) || types.IsTimespan(type2)) {
-		// MySQL allows time-related types to reference each other in foreign keys:
-		// - DATETIME can reference DATETIME with different precision
-		// - TIMESTAMP can reference TIMESTAMP with different precision
-		// - DATETIME can reference TIMESTAMP and vice versa
-		// - TIME can reference TIME with different precision
 		return true
 	}