[gdb/testsuite] Fix gdb.ada/mi_task_arg.exp with newer gcc

[gdb/testsuite] Fix gdb.ada/mi_task_arg.exp with newer gcc

When running test-case gdb.ada/mi_task_arg.exp on openSUSE Tumbleweed using
gcc 13.2.1, I run into (layout adapted for readability):
...
-stack-list-arguments 1^M
^done,stack-args=[
  frame={level="0",args=[]},
  frame={level="1",args=[{name="<_task>",value="0x464820"},
                         {name="<_taskL>",value="129"}]},
  frame={level="2",args=[{name="self_id",value="0x464840"}]},
  frame={level="3",args=[]},
  frame={level="4",args=[]}
]^M
(gdb) ^M
FAIL: gdb.ada/mi_task_arg.exp: -stack-list-arguments 1 (unexpected output)
...

On openSUSE Leap 15.4 with gcc 7.5.0 I get instead:
...
-stack-list-arguments 1^M
^done,stack-args=[
  frame={level="0",args=[]},
  frame={level="1",args=[{name="<_task>",value="0x444830"}]},
  frame={level="2",args=[{name="self_id",value="0x444850"}]},
  frame={level="3",args=[]},
  frame={level="4",args=[]}]^M
(gdb) ^M
PASS: gdb.ada/mi_task_arg.exp: -stack-list-arguments 1
...

The difference in gdb output is due to difference in the dwarf generated by
the compiler, so I don't see a problem with gdb here.

Fix this by updating the test-case to accept this output.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>