Disable test_preload_file_with_manual_data_download_pthreads under firefox (#19081)

See #19080

Author: sbc100

test/test_browser.py

@@ -422,6 +422,7 @@ def make_main_two_files(path1, path2, nonexistingpath):
     'pthreads': (['-pthread', '-sPROXY_TO_PTHREAD', '-sEXIT_RUNTIME'],),
   })
   @requires_threads
+  @no_firefox('https://github.com/emscripten-core/emscripten/issues/19080')
   def test_preload_file_with_manual_data_download(self, args):
     src = test_file('manual_download_data.cpp')