mypaint: fix build with Python 3.11

srcpkgs/mypaint/patches/python-3.11.patch

@@ -0,0 +1,11 @@
+--- a/setup.py
++++ b/setup.py
+@@ -632,7 +632,7 @@ class InstallScripts (install_scripts):
+         self.announce("installing %s as %s" % (src, targ_basename), level=2)
+         if self.dry_run:
+             return []
+-        with open(src, "rU") as in_fp:
++        with open(src, "r") as in_fp:
+             with open(targ, "w") as out_fp:
+                 line = in_fp.readline().rstrip()
+                 if line.startswith("#!"):