Change order of matplotlib imports (#546)

toolbox/ui.py

+import matplotlib.pyplot as plt
 from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
 from matplotlib.figure import Figure
 from PyQt5.QtCore import Qt, QStringListModel
@@ -8,7 +9,6 @@ from pathlib import Path
 from typing import List, Set
 import sounddevice as sd
 import soundfile as sf
-import matplotlib.pyplot as plt
 import numpy as np
 # from sklearn.manifold import TSNE         # You can try with TSNE if you like, I prefer UMAP 
 from time import sleep