Fix "Model Optimziation" typo

The typo causes menu issues, reported by a user.
Fixes pytorch/pytorch#111643

Author: kit1980

prototype_source/prototype_index.rst

@@ -97,7 +97,7 @@ Prototype features are not available as part of binary distributions like PyPI o
    :card_description: Prune BERT to be 2:4 sparse and accelerate for inference.
    :image: _static/img/thumbnails/cropped/generic-pytorch-logo.png
    :link: prototype/semi_structured_sparse.html
-   :tags: Model-Optimziation
+   :tags: Model-Optimiziation
 
 .. Mobile