Update README.md

Author: PierreBoyeau

README.md

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 # Multi-resolution Variational Inference
 
+**DEPRECIATED: please refer to the current [version](https://github.com/YosefLab/mrvi) of the project for up-to-date code**
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 Multi-resolution Variational Inference (MrVI) is a package for analysis of sample-level heterogeneity in multi-site, multi-sample single-cell omics data. Built with [scvi-tools](https://scvi-tools.org).
 
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