Audio Export - Solo function in the mixer does not affect the output file.

https://musescore.org/en/comment/902030#comment-902030

1.) Create or load a score with multiple instruments.
2.) In the mixer, click the "Solo" Button for one Instrument
3.) File->Export - as "File Type" chose "mp3" or "Wave" from the dropdown box
4.) When you listen to the resulting audio file, all instruments are being heard, instead of only the soloed instrument, as it should be (and was in version 2.xx)

The issue was reproduced by me with different scores.

OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 3.0.4.5763, revision: cda4080