According to Timatic you don't need a transit visa:
TWOV (Transit Without Visa):
Visa required, except for Holders of onward tickets for a max. transit time of 24 hours.
However:
Angola (AO)
Vaccination against yellow fever required.
Exempt from Yellow Fever vaccination:
- Children under 1 year of age.
- Passengers transiting Angola who do not leave the aircraft and continue their journey by the same aircraft.
