I want to remove iCloud two-way authentication factor

See the article Use two-factor authentication for security on your Mac, iOS devices, and iPadOS devices - Apple Support

Add or remove a trusted phone number

You must verify at least one trusted phone number to enroll in two-factor authentication.

1. On your Mac, choose Apple menu  > System Preferences, click Apple ID, then select Password & Security in the sidebar.
2. Click Edit, then do any of the following: 

• • To add a phone number, click the Add button . Enter your Mac login password. Enter a phone number that can be used to verify your identity. Select whether you want to be reached by text or phone call, then click Continue. Enter the code sent to the email address or phone number and click Next. Your trusted phone numbers appear in a list.
  • To remove an email or phone number, select a phone number, click the Delete button , then click Remove.

Do you remember the Apple ID and password for 2FA , is that single trusted number lost / damaged or you used some one else trusted number and the code goes to that number and you can't access it .

If you directly sign into www.icloud.com with account credentials definitely the code will go to that number that is not in your possession , but you have other ways to sign , click on get a verification code , the code will be displayed on Mac screen .

In password and security section , click on edit as shown in the screen shot , click on plus sign , the trusted numbers will be shown , you have to first add your trusted number and get it verified , then removed unwanted number authenticate the account with admin password .

See the article Change Password & Security preferences for your Apple ID on Mac - Apple Support

Not necessary you always sign in with appleid.apple.com with account credentials with your 2FA account , and change the trusted number , if you are using Mac change from system preferences location .

Make sure first you add desired working trusted number and it will be verified from this location , then delete ( click on subtract sign ) unwanted number .

Some users add at two leat trusted numbers it could be a mobile or a landline number .

Read Two-factor authentication for Apple ID - Apple Support

Get a verification code and sign in with two-factor authentication - Apple Support

To remove an alias from your iCloud account navigate to: https://appleid.apple.com/#!&page=signin