gdb/testsuite: fix list.exp test cases

PR testsuite/7142 -- old enough to have been converted from Gnats --
points out that test_list_filename_and_function in gdb.base/list.exp
has "fails" that are unmatched with passes.  This patch cleans this up
a little.

Co-authored-by: Tom Tromey <tromey@adacore.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=7142
1 file changed