TC-OPSTATE-2.5: Force expire session on reboot (project-chip#35712)

If the DUT has rebooted, the TH will need to establish the session
again, which means expiring the current. In a real product, a fail
on the case would trigger a retry, but it's not clear that we want
that in the TH because it can paper over problems where the DUT is
crashing. This is an intentional reboot, wihch is different.

Probably not caught in CI / QA because the CI app doesn't actually
reboot.

src/python_testing/TC_OpstateCommon.py

@@ -1112,10 +1112,11 @@ async def TEST_TC_OPSTATE_BASE_2_5(self, endpoint=1):
 
             # STEP 11: Restart DUT
             self.step(11)
-            # In CI environment, the STOP coommand (step 8) already resets the variables. Only ask for
+            # In CI environment, the STOP command (step 8) already resets the variables. Only ask for
             # reboot outside CI environment.
             if not self.is_ci:
                 self.wait_for_user_input(prompt_msg="Restart DUT. Press Enter when ready.\n")
+                self.default_controller.ExpireSessions(self.dut_node_id)
 
             # STEP 12: TH waits for {PIXIT.WAITTIME.REBOOT}
             self.step(12)