metadata factor levels are dropped, boxplot+heatmap

[KasperSkytte]

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If you encounter a problem with ampvis2 that you are unable to resolve, this is the place for discussing the problem with developers to find a solution. To best help you quickly, please first make sure that:

• you have the latest version of the package installed
• you have carefully read the documentation of the ampvis2 function(s) used
• you have searched the GitHub issues page or the internet for similar or identical problems

Should the problem still persist, then please provide a minimal reproducible example, preferably using reprex, with self-contained code so that anyone can copy the code and reproduce the problem to easily start debugging without further communication.

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