Update README.md

Author: devfans

README.md

@@ -42,7 +42,7 @@ python3 -m pip install electrum-scripting
 {'hex': '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', 'complete': False, 'final': False}
 
 # Other utils
-> ws.qr(tx, 'unsigned_tx.png')
+> ws.qr(tx, 'unsigned_tx.svg')
 
 ```