debian: remove stale distutils override from py3dist-overrides

debian: remove stale distutils override from py3dist-overrides

distutils was deprecated in Python 3.10 (PEP 632) and removed in
Python 3.12. The `python3-distutils` package no longer exists in
Debian Trixie (Python 3.13) or Ubuntu 24.04+ (Python 3.12).

The only runtime reference was in `debian/ceph-mgr.requires`, already
cleaned up by 3fb3f892aa3. This override is now dead code, hence no
installed file declares a runtime dependency on `distutils`, so
`dh_python3` never resolves it. Removing it prevents a latent
uninstallable-dependency bug if `distutils` were accidentally
reintroduced in a `.requires` file.

Fixes: https://tracker.ceph.com/issues/75901
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Signed-off-by: Max R. Carrara <m.carrara@proxmox.com>
Signed-off-by: Kefu Chai <k.chai@proxmox.com>