Update debugger.py

Author: LamentXU123

Lib/idlelib/debugger.py

@@ -1,6 +1,6 @@
 """Debug user code with a GUI interface to a subclass of bdb.Bdb.
 
-The Idb idb and Debugger gui instances each need a reference to each
+The Idb and Debugger gui instances each need a reference to each
 other or to an rpc proxy for each other.
 
 If IDLE is started with '-n', so that user code and idb both run in the