Stop generating empty .worker.js in pthreads builds

We stopped using a separate worker file back in #21701.  That was
released in 3.1.58 back in April.

This change ends the transition period by no longer generating a
dummy/useless worker.js file alongside the output.

Author: sbc100

test/test_other.py

@@ -14881,20 +14881,9 @@ def test_embind_no_duplicate_symbols(self):
     create_file('b.cpp', '#include <emscripten/bind.h>')
     self.run_process([EMXX, '-std=c++23', '-lembind', 'a.cpp', 'b.cpp'])
 
-  def test_legacy_pthread_worker_js(self):
-    self.do_runf('hello_world.c', emcc_args=['-pthread', '-sSTRICT'])
-    self.assertNotExists('hello_world.worker.js')
-    self.do_runf('hello_world.c', emcc_args=['-pthread'])
-    self.assertExists('hello_world.worker.js')
-    os.mkdir('out')
-    self.do_runf('hello_world.c', output_basename='out/foo', emcc_args=['-pthread'])
-    self.assertExists('out/foo.js')
-    self.assertExists('out/foo.worker.js')
-
   def test_no_pthread(self):
     self.do_runf('hello_world.c', emcc_args=['-pthread', '-no-pthread'])
     self.assertExists('hello_world.js')
-    self.assertNotExists('hello_world.worker.js')
     self.assertNotContained('Worker', read_file('hello_world.js'))
 
   def test_sysroot_includes_first(self):

tools/link.py

@@ -2073,15 +2073,6 @@ def phase_final_emitting(options, state, target, wasm_target):
     return
 
   target_dir = os.path.dirname(os.path.abspath(target))
-  if settings.PTHREADS and not settings.STRICT and not settings.SINGLE_FILE:
-    worker_file = shared.replace_suffix(target, get_worker_js_suffix())
-    write_file(worker_file, '''\
-// This file is no longer used by emscripten and has been created as a placeholder
-// to allow build systems to transition away from depending on it.
-//
-// Future versions of emscripten will likely stop generating this file at all.
-throw new Error('Dummy worker.js file should never be used');
-''')
 
   # Deploy the Wasm Worker bootstrap file as an output file (*.ww.js)
   if settings.WASM_WORKERS == 1: