The partial-tunnel deletion API was buggy and redundant:
* e.g. It erased entries from globGtp.te2ue_mapping but never erases
  the corresponding entries from inst->ue2te_mapping[ue].bearers

All current use cases are already covered by:
* newGtpuDeleteOneTunnel() for targeted deletion
* newGtpuDeleteAllTunnels() for full cleanup

Call sites should explicitly loop over newGtpuDeleteOneTunnel()
if multiple tunnels need removal.