Revert "Use response code 102 ("Processing") instead of 503 ("Service Unavailable") for the loading screen"

This reverts commit 8823f69256.

src/main/java/org/qortal/arbitrary/ArbitraryDataRenderer.java

@@ -153,7 +153,7 @@ public class ArbitraryDataRenderer {
         } catch (IOException e) {
             LOGGER.info("Unable to show loading screen: {}", e.getMessage());
         }
-        return ArbitraryDataRenderer.getResponse(response, 102, responseString);
+        return ArbitraryDataRenderer.getResponse(response, 503, responseString);
     }
 
     public static HttpServletResponse getResponse(HttpServletResponse response, int responseCode, String responseString) {