Widen the deployed_config_hash poll window: 10s wasn't always enough

Saw a real install (confirmed matching via a follow-up curl) get reported
as a false-negative failure because the 10x1s poll gave up too early.

tools/gxepd2_dashboard/dashboard.py

@@ -143,7 +143,7 @@ async def install(configuration: str, timeout: float = 480) -> bool:
             return False
 
     expected = device_status(configuration).get("expected_config_hash")
-    for _ in range(10):
+    for _ in range(20):
         dev = device_status(configuration)
         if dev.get("deployed_config_hash") == expected:
             print(f"deployed_config_hash confirmed: {expected}", flush=True)