[reference model] Code cleanup for SHAPE

remove unnecessary change of tensor shape array for SHAPE data type

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: I8e6ca98448188a1c30f9d29c22b3194d327b17ac
diff --git a/reference_model/src/tensor.h b/reference_model/src/tensor.h
index 74f57ed..fe7336d 100644
--- a/reference_model/src/tensor.h
+++ b/reference_model/src/tensor.h
@@ -812,11 +812,7 @@
                 }
                 break;
             case TOSA_REF_TYPE_SHAPE:
-                // if shape information is not already set, set it here.
-                if (shape_.size() == 0)
-                {
-                    shape_ = { 1 };
-                }
+                assert(rank == 0);
                 return new Tensor0<int64_t>(tensorName_, dtype_, shape_);
             case TOSA_REF_TYPE_BOOL:
                 switch (rank)