make less batch of tests to fit ci (#16706)

* make less batch of tests to fit ci

* test=develop, invoke ci

add some comments back

python/paddle/fluid/tests/unittests/test_imperative_transformer.py

@@ -302,11 +302,8 @@ use_py_reader = False
 # if we run sync mode
 sync = False
 
-if not core.is_compiled_with_cuda():
-    # how many batches we use
-    batch_num = 50
-else:
-    batch_num = 5
+# how many batches we use
+batch_num = 5
 
 np.random.seed = 1
 src_word_np = np.random.randint(