apparmor: Remove unnecessary size check when unpacking trans_table

The index into the trans_table has a max size of 2^24 bits which the
code was testing but this is unnecessary as unpack_array can only
unpack a table of 2^16 bits in size so the table unpacked will never
be larger than what can be indexed, and any test here is redundant.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>