[minor] README.md

PyLoT.py

@@ -3729,6 +3729,7 @@ class MainWindow(QMainWindow):
 
     def closeEvent(self, event):
         if self.okToContinue():
+            self.logwidget.close()
             event.accept()
         else:
             event.ignore()

README.md

@@ -42,7 +42,7 @@ In order to run PyLoT you need to install:
 (the following are already dependencies of the above packages):
 - scipy
 - numpy
-- matplotlib
+- matplotlib <= 3.3.x
 
 #### Some handwork: