gdb/testsuite: Remove use of dejagnu cleanup proc

The 'cleanup' proc has been removed from dejagnu (Feb 15 2016).  The
proc has not done anything useful since at least 2001 so removing
these calls should be harmless.

gdb/testsuite/ChangeLog:

	* config/sid.exp (gdb_target_sid): Remove use of cleanup.
	* config/sim.exp (gdb_target_sim): Remove use of cleanup.