If the receiver has BEC (Battery Eliminator Circuitry) in it, then you can safely input 7.2 volts. It will reduce the voltage fed to the servos down to 6 volts.
However, since that's 7.4v, I don't know how well the BEC would handle it over time. Especially since the BEC is actually a resistor, it might pass the servos something like 6.05v, which might be just a hair more than they can handle.
If your receiver has that feature, it will say on the label "BEC" or "Battery Eliminator Circuit".
If you cannot find it, then it may not be a wise idea to use the pack, as it will fry your servos. Perhaps contact the maker of the receiver and ask them as to the safest maximum voltage allowed?