Cannot reproduce your issue, I can setup the repo and install MongoDB Enterprise without issue. It looks like the wget of the GPG Publlic Key did not succeed in your command and output invalid data to the apt-key add -
Please use formatting when posting code and outputs.
It appears the current public key is valid up until February 2027 (and since February 20222)
root@bbe41aedd8e5:/# wget -qO - https://www.mongodb.org/static/pgp/server-6.0.asc | gpg
gpg: directory '/root/.gnupg' created
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: WARNING: no command supplied. Trying to guess what you mean ...
pub rsa4096 2022-02-23 [SC] [expires: 2027-02-22]
39BD841E4BE5FB195A65400E6A26B1AE64C3C388
uid MongoDB 6.0 Release Signing Key <packaging@mongodb.com>