chore: remove testnet

Author: reez

BDKSwiftExampleWallet/Resources/Localizable.xcstrings

@@ -671,6 +671,7 @@
       }
     },
     "Testnet" : {
+      "extractionState" : "stale",
       "localizations" : {
         "fr" : {
           "stringUnit" : {

BDKSwiftExampleWallet/View/OnboardingView.swift

@@ -77,16 +77,10 @@ struct OnboardingView: View {
                 }
                 .padding()
 
-                Picker(
-                    "Network",
-                    selection: $viewModel.selectedNetwork
-                ) {
-                    Text("Signet").tag(Network.signet)
-                    Text("Testnet").tag(Network.testnet)
-                }
-                .pickerStyle(.automatic)
-                .tint(.primary)
-                .accessibilityLabel("Select Bitcoin Network")
+                Text("Signet")
+                    .foregroundStyle(.primary)
+                    .fontWeight(.light)
+                    .accessibilityLabel("Select Bitcoin Network")
 
                 Picker(
                     "Esplora Server",