Update sentiment-analysis-model-builder.md

[MoziVi]

Correcting an incorrect extension used in the documentation related to a generated ML.NET model file.

Summary

While completing a tutorial, I noticed an incorrect file format and description in the documentation, so I fixed it accordingly.

Fixes #46585

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📄 File	🔗 Preview link
docs/machine-learning/tutorials/sentiment-analysis-model-builder.md	Tutorial: Analyze sentiment of website comments in a web application using ML.NET Model Builder