Fix dialog category label alignment
requested to merge VaibhavMalik4187/inkscape:dialog-notebook-category-label-alignment-fix into 1.4.x
Updating the label via the set_label method unexpectedly altered the alignment of the PopoverMenuItem label from Gtk::ALIGN_START to Gtk::ALIGN_FILL. This commit resolves this issue by replacing the original label with a new one to update its text while preserving the desired alignment.
Fixes #4925