Batch processing interrupted if sample rate too high for MP3 Export

[SteveDaulton]

Describe the bug
When batch processing, if the export format is MP3 and the sample rate of the file is too high for the selected MP3 options, or greater than 48 kHz, then batch processing is interrupted - prompting the user to manually enter a lower sample rate.

To Reproduce
Steps to reproduce the behavior:

1. Apply "MP3 Conversion" macro to "Files" and select a file that has a sample rate > 48 kHz.
2. Observe that the batch processing stops to ask for a lower sample rate.

Expected behavior
Audacity to automatically select an appropriate sample rate when MP3 encoding as a batch process.

Screenshots

Additional information (please complete the following information):

• OS: Xubuntu 20.04
• Version audacity-linux-3.0.4-x86_64.AppImage

Additional context
In most cases, the "suggested" sample rate of 8000 Hz is the worst possible option. Better to default to the highest supported sample rate rather than the lowest.

[SteveDaulton]

There is now an experimental plug-in that overcomes this limitation (https://forum.audacityteam.org/viewtopic.php?p=434518#p434518) but it would be better if the solution was built in rather than requiring an additional plug-in.