Fix typo in idlelib.config_key.py (#2322)

Author: terryjreedy

Lib/idlelib/config_key.py

@@ -186,7 +186,7 @@ def ClearKeySeq(self):
 
     def LoadFinalKeyList(self):
         #these tuples are also available for use in validity checks
-        self.functionKeys=('F1','F2','F2','F4','F5','F6','F7','F8','F9',
+        self.functionKeys=('F1','F2','F3','F4','F5','F6','F7','F8','F9',
                 'F10','F11','F12')
         self.alphanumKeys=tuple(string.ascii_lowercase+string.digits)
         self.punctuationKeys=tuple('~!@#%^&*()_-+={}[]|;:,.<>/?')