fix(mobile/routes): drop stale settings Stack.Screen declaration

The <Stack.Screen name="settings" /> declaration pointed at
the flat app/settings.tsx file, which was moved to
app/settings/index.tsx when we added sub-routes. Expo Router
logs a warning because no route with that exact name exists
any more. The sub-routes register themselves via file-based
routing so no explicit declaration is needed.

Author: Aqib-Rime

apps/mobile/app/_layout.tsx

@@ -72,7 +72,6 @@ export default function RootLayout() {
                 }}
               />
               <Stack.Screen name="qibla" />
-              <Stack.Screen name="settings" />
             </Stack>
           </Providers>
         </SafeAreaProvider>