Summary:
Remove memory check for node-agent check in YNP
`MemoryCurrent` for systemctl is set only while using cgroups v2. Removing this check so as to remove OS specific dependency

Test Plan: Manual Testing

Reviewers: skhilar, nbhatia

Reviewed By: skhilar

Differential Revision: https://phorge.dev.yugabyte.com/D44008