wrong variable name used (#4328)

model_cards/google/electra-base-generator/README.md

@@ -25,7 +25,7 @@ fill_mask = pipeline(
 )
 
 print(
-	fill_mask(f"HuggingFace is creating a {nlp.tokenizer.mask_token} that the community uses to solve NLP tasks.")
+	fill_mask(f"HuggingFace is creating a {fill_mask.tokenizer.mask_token} that the community uses to solve NLP tasks.")
 )
 
 ```