Remove useless mapRequest tracking that just effects Qt display.

I thought we had removed this a long time ago, TBH, its really
confusing feedback to users that we display whether a tx was
broadcast to immediate neighbor nodes, given that has little
indication of whether the tx propagated very far.

src/interfaces/wallet.h

@@ -346,7 +346,6 @@ struct WalletTxStatus
     int block_height;
     int blocks_to_maturity;
     int depth_in_main_chain;
-    int request_count;
     unsigned int time_received;
     uint32_t lock_time;
     bool is_final;