Remove group entries from cloud.cfg.tmpl

# Bug report
Issue #4603 has highlighted that cloud-init is creating any distro-specific groups defined in /etc/cloud/cloud.cfg.tmpl on system where they are not already present on the system as non-system groups (i.e. gids > 999). However the groups defined in the template file all appear to be typical system groups rather than "normal" groups.

Therefore I think we should remove these group definitions to avoid them being incorrectly created (with wrong gids).

## Steps to reproduce the problem
Run cloud-init on a distro where one of the distro-specific groups in cloud.cfg/cloud.cfg.tmpl is missing (see #4603 for an example)

## Environment details
- Cloud-init version: all versions
- Operating System Distribution: any
- Cloud provider, platform or installer type: any

## cloud-init logs