Fix README: double way to cite fhEVM

[bcm-at-zama]

Please remove the

@techreport{fhEVM,
author = "Zama",
title = "Confidential EVM Smart Contracts using Fully Homomorphic Encryption",
institution = "Zama",
year = "2024"
}

in the README.md, to avoid a double way to cite in the README.

[bcm-at-zama]

Seems like I have not the rights to do it, and @aquint-zama is off for a few days