Lilac master: The following signatures were invalid: EXPKEYSIG 68818C72E52529D4 MongoDB 4.0 Release Signing Key

Hello Everyone,
I am installing lilac openedx version on ubuntu 20.04 according to openedx documentation and getting error can’t install mongodb 4.0 on ubuntu 20.04. Can you help me through this step?
As far as I know, ubuntu keyserver for mongodb 4.0 can only be installed on ubuntu 16.04 instance.
Link: 3.2.2. Lilac Open edX Native Installation — Installing, Configuring, and Running the Open edX Platform: Lilac Release documentation
tags: configuration/util/install at open-release/lilac.master · openedx/configuration · GitHub

TASK [server_utils : Install ubuntu system packages] ***************************
fatal: [localhost]: FAILED! => {"changed": false, "msg": "Failed to update apt cache: W:Updating from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., W:GPG error: http://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 Release: The following signatures were invalid: EXPKEYSIG 68818C72E52529D4 MongoDB 4.0 Release Signing Key <packaging@mongodb.com>, E:The repository 'http://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 Release' is not signed."}

PLAY RECAP *********************************************************************
localhost                  : ok=5    changed=1    unreachable=0    failed=1    skipped=99   rescued=0    ignored=0   

 
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Ansible failed!
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Decoded error:
== msg ===========================
Failed to update apt cache: W:Updating from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., W:GPG error: http://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 Release: The following signatures were invalid: EXPKEYSIG 68818C72E52529D4 MongoDB 4.0 Release Signing Key <packaging@mongodb.com>, E:The repository 'http://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 Release' is not signed.
 
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Installation failed!
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If you need help, see https://open.edx.org/getting-help .
When asking for help, please provide as much information as you can.
These might be helpful:
    Your log file is at /home/server/logs/install-20230524-032707.log
    Your environment:
        OPENEDX_RELEASE=open-release/lilac.master
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Installation finished at 2023-05-24 03:29:02