Correct model size in model card

the model is `state-spaces/mamba-130m-hf` but the model card says "This repository contains the `transfromers` compatible `mamba-2.8b`". Simple change to reflect the fact that this is (or should be) the `mamba-130m` model.

README.md

@@ -6,7 +6,7 @@ tags: []
 # Mamba
 
 <!-- Provide a quick summary of what the model is/does. -->
-This repository contains the `transfromers` compatible `mamba-2.8b`. The checkpoints are untouched, but the full `config.json` and tokenizer are pushed to this repo. 
+This repository contains the `transfromers` compatible `mamba-130m`. The checkpoints are untouched, but the full `config.json` and tokenizer are pushed to this repo. 
 
 # Usage