debian: Do not remove swtpm_cuse.8 via clean file

swtpm_cuse.8 is not generated anymore but its a static file now
that must not be removed anymore via the debian/clean file.

Resolves: https://github.com/stefanberger/swtpm/issues/751
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
1 file changed