s1gw_metrics: remove ?S1GW_{CTR,GAUGE}_S1AP_PROXY_UPLINK_PACKETS_QUEUED
We no longer queue any packets, so these metrics are not relevant.
Change-Id: I6c4c4a751dbe5a245f16515a1a1d65acf33468e9
Related: 4614fc3 ("s1ap_proxy: move S1 SETUP handling to sctp_proxy")
Related: SYS#7052
