[lldb/tests] Removed add_test_categories decorator for python API tests, NFC

There is a .categories file in the python_api directory that makes all nested tests
belong to the category "pyapi". The decorator is unnecessary for these tests.

lldb/test/API/python_api/sbstructureddata/TestStructuredDataAPI.py

@@ -18,7 +18,6 @@ class TestStructuredDataAPI(TestBase):
     def test(self):
         self.structured_data_api_test()
 
-    @add_test_categories(['pyapi'])
     def structured_data_api_test(self):
         error = lldb.SBError()
         s = lldb.SBStream()