Fix HermesWsClientTest teardown and OkHttp 5.x deprecation warnings

- Widen catch in tearDown() from Exception to Throwable so
  MockWebServer.shutdown() AssertionError is caught (OkHttp 5.x
  enforces clean connection state on shutdown)
- Increase teardown wait from 100ms to 500ms for WS close handshake
- Replace deprecated RequestBody.create(null, ...) with
  toRequestBody() extension from Kotlin API

app/src/main/java/com/m57/hermescontrol/data/ws/HermesWsClient.kt

@@ -25,7 +25,9 @@ import kotlinx.coroutines.launch
 import okhttp3.CertificatePinner
 import okhttp3.OkHttpClient
 import okhttp3.Request
+import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.RequestBody
+import okhttp3.RequestBody.Companion.toRequestBody
 import okhttp3.Response
 import okhttp3.WebSocket
 import okhttp3.WebSocketListener
@@ -166,7 +168,7 @@ object HermesWsClient {
                 Request.Builder()
                     .url("http://${AuthManager.getHost()}:${AuthManager.getPort()}/api/auth/ws-ticket")
                     .header("Cookie", "hermes_session_at=$sessionCookie")
-                    .post(RequestBody.create(null, "{}"))
+                    .post("{}".toRequestBody())
                     .build()
             val response = client.newCall(request).execute()
             if (response.isSuccessful) {