[lldb-dap][test] fix not supported error. (#144419)

Fixes #144072 

buildbot error.

Author: da-viper

lldb/test/API/tools/lldb-dap/stepInTargets/TestDAP_stepInTargets.py

@@ -112,7 +112,13 @@ def test_supported_capability_other_archs(self):
             len(breakpoint_ids), len(bp_lines), "expect correct number of breakpoints"
         )
         self.continue_to_breakpoints(breakpoint_ids)
-        is_supported = self.dap_server.get_capability("supportsStepInTargetsRequest")
+
+        try:
+            is_supported = self.dap_server.get_capability(
+                "supportsStepInTargetsRequest"
+            )
+        except dap_server.NotSupportedError:
+            is_supported = False
 
         self.assertEqual(
             is_supported,