Update MLM usage

sections/mlm_usage.md

@@ -1,4 +1,4 @@
-- This demo loads the `FlaxCLIPVisionBertForMaskedLM` present in the `model` directory of this repository. The checkpoint is loaded from [`flax-community/clip-vision-bert-cc12m-70k`](https://huggingface.co/flax-community/clip-vision-bert-cc12m-70k) which is pre-trained checkpoint with 70k steps. 
+- This demo loads the `FlaxCLIPVisionBertForMaskedLM` present in the `model` directory of this repository. The checkpoint is loaded from [`flax-community/clip-vision-bert-cc12m-60k`](https://huggingface.co/flax-community/clip-vision-bert-cc12m-60k) which is pre-trained checkpoint with 60k steps. 
 
 - 100 random validation set examples are present in the `cc12m_data/vqa_val.tsv` with respective images in the `cc12m_data/images_data` directory.