feat: use single charge endpoint for balance

lnbits/extensions/satspay/templates/satspay/display.html

@@ -323,10 +323,9 @@
         try {
           const {data} = await LNbits.api.request(
             'GET',
-            `/satspay/api/v1/charges/balance/${this.charge.id}`,
+            `/satspay/api/v1/charge/balance/${this.charge.id}`,
             'filla'
           )
-
           this.charge.time_elapsed = data.time_elapsed
           this.charge.amount = data.amount
           this.charge.balance = data.balance