[MusicXML import] incorrect handling of sequentially numbered non-overlapping part-groups

File "An American Requiem - Rev2.mxl", a direct export by Sibelius 7.5.1attached to https://musescore.org/en/node/334128 contains a number of non-overlapping part-groups numbered 1 up to 6.

This is not correct according to the "number" description in https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/part-….

As MuseScore's MusicXML importer simply copies the number (minus one) into the bracket's "column" parameter, this results in too much space between the brackets and the part name. Workaround is to use the inspector to correct the column parameter.