How to convert 3.3V from Raspberry Pi to usein a Remote Control Car which needs 3V
I think the additional 0.3V won't bite.

Should you really be concerned about this you can get a Schottky rectifier like 1N5819 to drop the voltage by 0.2V.

By the way 1N5819 are so cheap that you can get boxes of thousand for a few bucks - you can get a few hundred of those and start replacing 1N4001's in your circuits with those, and in some circuitry its lower forward drop means better efficiency.