Fix: remove redundant stopRedirectServer() call from ensureWebServer()

When the "start ota" command was issued from the web panel, a race
condition could occur between the main loop thread and the HTTP server
thread:

- HTTP thread: prepareForOTAStart() -> stopRedirectServer() ->
  httpd_stop(_redirect_server) [blocking]
- Main thread: loop() -> ensureWebServer() -> stopRedirectServer() ->
  httpd_stop(_redirect_server) [double free!]

Because stopRedirectServer() sets _redirect_server = nullptr only after
httpd_stop() returns, both threads could pass the nullptr check
simultaneously, resulting in a double free and heap corruption:

  CORRUPT HEAP: Bad head at 0x3fcb1f24. Expected 0xabba1234 got 0x3fca5f34
  assert failed: multi_heap_free multi_heap_poisoning.c:259 (head != NULL)

The call in ensureWebServer() was added as a safety net in commit
4b83142b, but is redundant: prepareForOTAStart() already calls
stopRedirectServer() synchronously before startOTAUpdate() occupies
port 80. Removing it eliminates the race condition.

The bug only manifested when OTA was triggered from the web panel
(HTTP thread), not from radio (main thread), because in the latter
case both calls happen on the same thread and cannot race.

src/helpers/web/WebService.cpp

@@ -103,9 +103,6 @@ void WebService::ensureWebServer() {
     return;
   }
   if (_suspended_for_ota) {
-    if (_panel.isRunning()) {
-      _panel.stopRedirectServer();
-    }
     return;
   }
   if (_panel.isRunning()) {