FS resize

This tutorial should include the information you need: https://access.redhat.com/documenta...gical_volume_manager_administration/lv_reduce

You should have a backup of your data volume, just in case, since there is a slight possibility of this going wrong. Additionally, since it is not explicitly mentioned in the tutorial I linked, you should unmount the FS before resizing, since it cannot be done online. This would mean that any running VMs should be stopped before this. If you want them to keep running during the resize process, you would have to migrate them away meanwhile.
 
caution: shrinking thin pools is not really possible, so depending on what 'pve-data' actually is, the linked guide may not work correctly