[pyright] remove no longer needed assertion

The pyright bug[1] for which the assertion was added has been fixed.

[1]: https://github.com/microsoft/pyright/issues/2930

package.json

@@ -1,6 +1,6 @@
 {
   "dependencies": {
     "eslint": "^8.7.0",
-    "pyright": "^1.1.212"
+    "pyright": "^1.1.215"
   }
 }

searx/webapp.py

@@ -1147,8 +1147,6 @@ def image_proxy():
             except httpx.HTTPError:
                 logger.exception('HTTP error on closing')
 
-    assert resp is not None
-
     def close_stream():
         nonlocal resp, stream
         try: