[test] Remove no-longer-needed v8 flags. NFC (#25683)

Author: sbc100

test/test_core.py

@@ -141,7 +141,6 @@ def decorated(self, *args, **kwargs):
       self.skipTest('SIMD tests are too slow with -O3 in the new LLVM pass manager, https://github.com/emscripten-core/emscripten/issues/13427')
     self.cflags.append('-msimd128')
     self.cflags.append('-fno-lax-vector-conversions')
-    self.v8_args.append('--experimental-wasm-simd')
     return func(self, *args, **kwargs)
   return decorated
 

test/test_other.py

@@ -13411,7 +13411,6 @@ def test_unsafe_optimizations(self):
 
   @requires_v8
   def test_extended_const(self):
-    self.v8_args += ['--experimental-wasm-extended-const']
     # Export at least one global so that we exercise the parsing of the global section.
     self.do_runf('hello_world.c', cflags=['-sEXPORTED_FUNCTIONS=_main,___stdout_used', '-mextended-const', '-sMAIN_MODULE=2'])
     wat = self.get_wasm_text('hello_world.wasm')
@@ -13477,10 +13476,6 @@ def test_jspi_code_size(self):
 
     self.run_process([EMXX, 'main.cpp', '-sASYNCIFY=2'] + shared_args)
 
-    # enable stack switching and other relevant features (like reference types
-    # for the return value of externref)
-    self.v8_args.append('--experimental-wasm-stack-switching')
-
     self.assertContained(expected, self.run_js('a.out.js'))
     stack_switching_size = os.path.getsize('a.out.wasm')