Update first occurrence of QT to show both 4 and 5

Arthur-Milchior · web-flow · commit 090ffea07d6b · 2021-01-05T13:40:25.000+01:00
As a newcommer to matplotlib, I was surprised to see only qt4. I quickly saw that qt5 is also supported and I believe it should be listed.
I don't know enough to know whether "How do I select PyQt4 or PySide?" section should also be updated
diff --git a/tutorials/introductory/usage.py b/tutorials/introductory/usage.py
@@ -281,7 +281,7 @@ def my_plotter(ax, data1, data2, param_dict):
 # "frontend" is the user facing code, i.e., the plotting code, whereas the
 # "backend" does all the hard work behind-the-scenes to make the figure.
 # There are two types of backends: user interface backends (for use in
-# pygtk, wxpython, tkinter, qt4, or macosx; also referred to as
+# pygtk, wxpython, tkinter, qt4, qt5, or macosx; also referred to as
 # "interactive backends") and hardcopy backends to make image files
 # (PNG, SVG, PDF, PS; also referred to as "non-interactive backends").
 #

Original file line number	Diff line number	Diff line change
`@@ -281,7 +281,7 @@ def my_plotter(ax, data1, data2, param_dict):`
`281`	`281`	`# "frontend" is the user facing code, i.e., the plotting code, whereas the`
`282`	`282`	`# "backend" does all the hard work behind-the-scenes to make the figure.`
`283`	`283`	`# There are two types of backends: user interface backends (for use in`
`284`		`-# pygtk, wxpython, tkinter, qt4, or macosx; also referred to as`
	`284`	`+# pygtk, wxpython, tkinter, qt4, qt5, or macosx; also referred to as`
`285`	`285`	`# "interactive backends") and hardcopy backends to make image files`
`286`	`286`	`# (PNG, SVG, PDF, PS; also referred to as "non-interactive backends").`
`287`	`287`	`#`