Can Cognito be configured to not require email verification when users sign up?

I believe this is related to the selection of MFA and/or your options for which attributes you want to verify for purposes of self-recovery of forgotten passwords. Under "MFA and verifications" on the Cognito user pool's console do you have "no verification" selected? If not, try that selecting "No verification."

On the Cognito dashboard under attribute verification it says: "Verification requires users to retrieve a code from their email or phone to confirm ownership. Verification of a phone or email is necessary to automatically configure users and enable recovery from forgotten passwords." Note that if you go with the "no verification" option then users may not be able to reset their own passwords, which may not be what you want.

You could also consider to automatically confirm users from a registered domain (see link below): https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-pre-sign-up.html

Hope this helps.