Reduce QTrio version repetition

Shouldn't be needed in pip >= 21.1.

pypa/pip#9437
pypa/pip#8785
pypa/pip#9775

setup.cfg

@@ -20,8 +20,6 @@ install_requires =
     attrs ~=20.3.0
     click ~=7.1
     pymodbus @ https://github.com/altendky/pymodbus/archive/83bf25071bdf56ece257e2e113a63dccf6bd692a.zip
-    # TODO: Should not need to duplicate the QTrio version info down below.
-    #       https://github.com/pypa/pip/issues/9437
     # >=0.4.1 for https://github.com/altendky/qtrio/pull/211
     qtrio ~=0.4.1
     # TODO: Uncomment whenever we get to using sundog here.
@@ -37,14 +35,10 @@ pyqt5 =
     # !=5.15.4 for https://github.com/altendky/ssst/issues/47
     #     it only really applies to macOS but i wasn't able to restrict to that
     pyqt5 ~=5.15, !=5.15.4
-    # TODO: Should not need to duplicate the QTrio version info from above.
-    #       https://github.com/pypa/pip/issues/9437
-    qtrio[pyqt5] ~=0.4.1
+    qtrio[pyqt5]
 pyside2 =
     pyside2 ~=5.15
-    # TODO: Should not need to duplicate the QTrio version info from above.
-    #       https://github.com/pypa/pip/issues/9437
-    qtrio[pyside2] ~=0.4.1
+    qtrio[pyside2]
 both =
     %(pyqt5)s
     %(pyside2)s