remove never-used get_result_cursor_strategy() method

remove never-used get_result_cursor_strategy() method

This method I would assume got committed during the
1.4 engine refactor, where we moved from different kinds of
ResultProxy implementations to different strategy
classes instead.   These strategies are set up by
dialects by setting "self.cursor_fetch_strategy"
in the execution context.   The method here was
likely a previous iteration of that which got merged
but was never used.

Change-Id: Iec292428f41c2c245bf7ae78beaa14786c28846c
(cherry picked from commit ec4a4910aa9ecc516cf3b096cb053fd9be7f82cc)