Demote "Document not focused" error from Electron

Summary: Comes from Electron. Will go away with PWA.

Reviewed By: lblasa

Differential Revision: D48778132

fbshipit-source-id: 0cecdc38e76b663315434aec995635afca2959dc

desktop/flipper-common/src/utils/LoggerTailer.tsx

@@ -74,6 +74,11 @@ function transformLogLevel(level: LoggerTypes, message: string) {
     if (message.includes('Watchman was not found in PATH')) {
       return 'warn';
     }
+
+    // Random Electron error, not actionable.
+    if (message.includes('Document is not focused')) {
+      return 'warn';
+    }
   }
 
   return level;