Needs to be updated to fix 404 error

[koolaidxk1d]

Line 225 in the serial generator script needs to be changed to
https://gitlab.com/wireshark/wireshark/-/blob/master-2.4/manuf

because the wireshark master branch no longer contains the manuf file.

[sickcodes]

Thanks, fixed via #30. Apologies for not getting this earlier, had been a busy few months