Fix type in @also_with_modularize test decorator. NFC

This was added incorrectly in #24555

Author: sbc100

test/common.py

@@ -683,7 +683,7 @@ def also_with_modularize(f):
   @wraps(f)
   def metafunc(self, modularize, *args, **kwargs):
     if modularize:
-      if '-sWASM_ESM_INTEGRATION':
+      if '-sWASM_ESM_INTEGRATION' in self.cflags:
         self.skipTest('also_with_modularize is not compatible with WASM_ESM_INTEGRATION')
       self.cflags += ['--extern-post-js', test_file('modularize_post_js.js'), '-sMODULARIZE']
     f(self, *args, **kwargs)