testsuite: Remove extra \n from expected output of tsv notifications

Commit 2450ad54 removed extra trailing \n from tsv notifications but
did not update gdb.trace/mi-tsv-changed.exp accordingly. This commit
removes the extra \n from expected output so gdb.trace/mi-tsv-changed.exp
passes again.

gdb/testsuite/ChangeLog:

	* gdb.trace/mi-tsv-changed.exp (test_create_delete_modify_tsv):
	Remove trailing \n from expected output.