The REQUEST_INSTALL_PACKAGES permission allowed your app to install packages.
To use this permission, the primary functionality of your app (the primary purpose of the app) must include:
send or receive app packets and
Enable the user to start the process of installing application packages
Allowed jobs include:
Web Browsing
Search or Google Assistant service
Communication services that allow the use of attachments
Share, move, or manage files
Enterprise Device Management
If your app doesn't meet these requirements, remove them from your app's manifest file to comply with Google Play policy.