Remove unnecessary False arg when constructing wx.App.

The arg has always defaulted to False in wx4
(https://wxpython.org/Phoenix/docs/html/wx.App.html#wx.App.__init__ +
scavenging git history), and unless you are well-versed in the wxPython
API it is not clear what it means.

Author: anntzer

lib/matplotlib/backends/backend_wx.py

@@ -1400,7 +1400,7 @@ def new_figure_manager(cls, num, *args, **kwargs):
         # Create a wx.App instance if it has not been created so far.
         wxapp = wx.GetApp()
         if wxapp is None:
-            wxapp = wx.App(False)
+            wxapp = wx.App()
             wxapp.SetExitOnFrameDelete(True)
             cbook._setup_new_guiapp()
             # Retain a reference to the app object so that it does not get