Your game statistics are replaced.
This includes your racial traits. Game statistics here refers to everything mechanical about your character. That is, all of your racial traits, class features, ability scores, everything. We see this explained for NPCs in the Monster Manual:
A monster’s statistics, sometimes referred to as its stat block, provide the essential information that you need to run the monster.
But this applies to PCs as well - your statistics are everything that make you, well, you, within the calculus of the game rules. In the Player’s Handbook, we have reference to game statistics in the step by step character creation section:
Your character is a combination of game statistics, roleplaying hooks, and your imagination.
So your racial traits are “game statistics”, and are replaced when you polymorph. You’re a giant ape, not an elf, so you do not get advantage on the saving throw.