[gdb/testsuite] Fix gdb.tui/basic.exp for TERM=ansis

[gdb/testsuite] Fix gdb.tui/basic.exp for TERM=ansis

With test-case gdb.tui/basic.exp and TERM=ansis, I run into (with some logging
added):
...
status line: '<reverse:1><intensity:dim>exec No process (asm) In:
             L??   PC: ?? <reverse:0><intensity:normal>'
FAIL: gdb.tui/basic.exp: status window: reverse
...

The status window uses ncurses attribute standout, which can differ between
different terminal settings.

Fix this by making the matching less strict.

Tested on x86_64-linux.