Fix readme

README.md

@@ -52,7 +52,7 @@ for t in text:
 Our training corpus consists of the Japanese portions of publicly available corpus such as C4, CC-100, and Oscar.
 We also incorporated the Web texts crawled by in-house system.
 The total size of our training corpus is about 650 GB.
-The trained model achieves 7.50 perplexity on the internal validation sets of Japanese C4,
+The trained model achieves 7.50 perplexity on the internal validation sets of Japanese C4.
 
 ## Tokenization
 We use a sentencepiece tokenizer with a unigram language model and byte-fallback.