Remove the old definition tests

The reason for this is that they haven't been used in years and don't really
make sense, because the way we now resolve parentheses is by executing the
result.

IMO this was a good patch at the time, but doesn't make sense anymore. Let me
know if you disagree ~dave.

test/completion/definition.py

@@ -1,68 +0,0 @@
-"""
-Fallback to callee definition when definition not found.
-- https://github.com/davidhalter/jedi/issues/131
-- https://github.com/davidhalter/jedi/pull/149
-"""
-
-"""Parenthesis closed at next line."""
-
-# Ignore these definitions for a little while, not sure if we really want them.
-# python <= 2.5
-
-#? isinstance
-isinstance(
-)
-
-#? isinstance
-isinstance( 
-)
-
-#? isinstance
-isinstance(None,
-)
-
-#? isinstance
-isinstance(None, 
-)
-
-"""Parenthesis closed at same line."""
-
-# Note: len('isinstance(') == 11
-#? 11 isinstance
-isinstance()
-
-# Note: len('isinstance(None,') == 16
-##? 16 isinstance
-isinstance(None,)
-
-# Note: len('isinstance(None,') == 16
-##? 16 isinstance
-isinstance(None, )
-
-# Note: len('isinstance(None, ') == 17
-##? 17 isinstance
-isinstance(None, )
-
-# Note: len('isinstance( ') == 12
-##? 12 isinstance
-isinstance( )
-
-"""Unclosed parenthesis."""
-
-#? isinstance
-isinstance(
-
-def x(): pass  # acts like EOF
-
-##? isinstance
-isinstance( 
-
-def x(): pass  # acts like EOF
-
-#? isinstance
-isinstance(None,
-
-def x(): pass  # acts like EOF
-
-##? isinstance
-isinstance(None,