If it has been two weeks or less since you enabled it, you can turn it off. If you are past that two week threshold, you can not turn it off.
Two-factor authentication for Apple ID - Apple Support
Can I turn off two-factor authentication after I’ve turned it on?
If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, you can unenroll within two weeks of enrollment. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require higher security.