pythongh-112938: IDLE - revert '_idletasks' addition in outwin

pythongh-88496 replaced text.update with text.update_idletasks
in two files to fix test failures on macOS.  While
theoretically correct, the result was Shell freezing when
receiving continuous short strings to print.

The guess is that there was no idle time in which to do
the screen update.  Reverting the change in one of the files,
outwin, fixes the issue.

The test will be patched as needed on macOS.

Lib/idlelib/outwin.py

@@ -112,7 +112,7 @@ def write(self, s, tags=(), mark="insert"):
         assert isinstance(s, str)
         self.text.insert(mark, s, tags)
         self.text.see(mark)
-        self.text.update_idletasks()
+        self.text.update()
         return len(s)
 
     def writelines(self, lines):