Answer: All of the people talked to said they would donate to the charity event.
Explanation:
Gender bias simply means a discrimination with regards to gender. Therefore the statement "Every person talked to said he would donate to the charity event" can be turned to " All of the people talked to said they would donate to the charity event" in order to remove the gender bias.
In this case, the gender bias has been removed as there isn't any"he" or "she" in the sentence and also because one isn't discriminating against the other.