That syntax requires MATLAB R2018a. In most situations there is no need to pre-allocate a table. Just construct it from efficiently created columns of data. If we knew more about where your data was coming from we might suggest alternative allocation/creation methods.
Pre-allocation of complex MATLAB structures and objects causes much confusion and is often not needed. Pre-allocate simple things (like numeric matrices or the top level of a cell array structure). Compound objects contain any number of individual contiguous simple data structures and do not need pre-allocation in general.
Read this answer discussing object pre-allocation for way to much (most of it good and correct) information on pre-allocation.