common: Remove superfluous assert
common: Remove superfluous assert

[why]
Modern compilers issue a warning, if you try to compare an unsigned
number with >=0, as this is always true. Unsigned ints can not carry
negative values.

[how]
Remove the assert and believe the type.

Signed-off-by: Fini Jastrow <df99dd64f50b60821f71f66742e94ffc417386fd@desy.de>

ulfjack/ryu,ulfjack/ryu,ulfjack/ryu,ulfjack/ryu