Step 1. Disable SIP. Boot into Recovery Mode. Open Terminal, type this and hit Enter
csrutil disable
Step 2. Reboot into Recovery Mode again. Open Terminal, using these commands
mount -uw /Volumes/{name of your macOS volume}
cd /Volumes/{name of your macOS volume}/
rm /System/Library/LaunchAgents/com.apple.ManagedClient*
rm /System/Library/LaunchDaemons/com.apple.ManagedClient*
# or back it up if you like, but I think you can completely remove it without harm.
Step 3. Enable SIP again.
csrutil enable
Done.