Modify test expression to avoid numerical differences (#2402).

(cherry picked from commit ae86a146b1ac9a49bf72e485254c08d237fd094a)

unsupported/test/cxx11_tensor_block_eval.cpp

@@ -244,7 +244,7 @@ static void test_eval_tensor_binary_with_unary_expr_block() {
   rhs.setRandom();
 
   VerifyBlockEvaluator<T, NumDims, Layout>(
-      (lhs.square() + rhs.square()).sqrt(),
+      (lhs.abs() + rhs.abs()).sqrt(),
       [&dims]() { return RandomBlock<Layout>(dims, 1, 10); });
 }