[lldb][lldb-dap][test] Disable part of TestDAP_launch on Arm 32-bit

This test has been flakey on our bot:
https://lab.llvm.org/buildbot/#/builders/18/builds/20410

```
======================================================================
FAIL: test_extra_launch_commands (TestDAP_launch.TestDAP_launch)
    Tests the "launchCommands" with extra launching settings
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/test/API/tools/lldb-dap/launch/TestDAP_launch.py", line 482, in test_extra_launch_commands
    self.verify_commands("stopCommands", output, stopCommands)
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py", line 228, in verify_commands
    self.assertTrue(
AssertionError: False is not true : verify 'frame variable' found in console output for 'stopCommands'
Config=arm-/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/bin/clang
----------------------------------------------------------------------
```

Likely a timing issue waiting for the command output on a slower
machine.

General tracking issue - llvm/llvm-project#137660

Author: DavidSpickett

lldb/test/API/tools/lldb-dap/launch/TestDAP_launch.py

@@ -431,6 +431,8 @@ def test_commands(self):
         self.verify_commands("exitCommands", output, exitCommands)
         self.verify_commands("terminateCommands", output, terminateCommands)
 
+    # Flakey on 32-bit Arm Linux.
+    @skipif(oslist=["linux"], archs=["arm$"])
     def test_extra_launch_commands(self):
         """
         Tests the "launchCommands" with extra launching settings