gdb/testsuite: check the correct Python variable in test

gdb/testsuite: check the correct Python variable in test

While squashing duplicate test names I spotted what looked like a copy
& paste error.  During this test a Python variable is created, and
then we call the type method on that variable.  In one case we create
a variable and then call the type method on a variable created for a
previous test.  I can see no reason why this should be what we want,
it doesn't line up with the comments in the test script, so I've
updated the test.  Note, the expected result doesn't change, just the
command issued (the test relates to stripping typedefs).

gdb/testsuite/ChangeLog:

	* gdb.python/lib-types.exp: Update the test to check the correct
	python variable.