debian: remove obsolete dependency
debian: remove obsolete dependency

This should fix package build for Ubuntu 17.04: obsolete package
hardening-wrapper was removed which cause .deb build failure.
The dependency on it is incorrect to begin with because we use
DEB_BUILD_MAINT_OPTIONS instead.

Change-Id: I3ea72b4123a280a846086d083c4f3189d611f8cf

osmocom/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx