[system-a] remove TensorRankAbove2 and TensorRankAbove1

- it is not good to limit input tensor, function should be fully extended

src/system-a/tensor/assertions.ts

@@ -8,18 +8,14 @@ export function assertScalar(t: any): asserts t is Scalar {
   }
 }
 
-export type TensorRankAbove1 = Array<Tensor>
-
-export function assertTensorRankAbove1(x: any): asserts x is TensorRankAbove1 {
+export function assertTensorRankAbove1(x: any): asserts x is Array<Tensor> {
   if (x instanceof Array && x.every(isTensor)) {
     return
   }
 
   throw new Error(`[assertTensorRankAbove1] ${x}`)
 }
 
-export type TensorRankAbove2 = Array<Array<Tensor>>
-
 export function assertTensorAlmostEqual(
   x: Tensor,
   y: Tensor,