What rhetorical device is "you don't have to be an Einstein to ..."

Metonymy

Explanation:

Metonymy is a rhetorical device that substitutes the name of an attribute for that of the thing meant.

An example is using a suit to represent a business executive.

"you don't have to be an Einstein to ... "

Albert Einstein is a famous scientist and inventor that is regarded as a genius. So the word genius and Einstein are used interchangeably.

That line can be translated as "you don't have to be a genius to ..."