remove outdated code in conv3d (#5696)

* remove experimental

* add test num

Co-authored-by: oneflow-ci-bot <69100618+oneflow-ci-bot@users.noreply.github.com>

python/oneflow/nn/modules/conv.py

@@ -659,7 +659,7 @@ class Conv3d(Module):
                         groups=1,
                     )
                 )
-            res = flow.experimental.cat(out_list, dim=in_channel_axis)
+            res = flow.cat(out_list, dim=in_channel_axis)
         else:
             res = flow.F.conv3d(
                 x,

python/oneflow/test/modules/test_conv3d.py

@@ -21,7 +21,7 @@ from automated_test_util import *
 
 @flow.unittest.skip_unless_1n1d()
 class TestConv3DModule(flow.unittest.TestCase):
-    @autotest(n=2)
+    @autotest(n=10)
     def test_conv3d_with_random_data(test_case):
         channels = random(1, 6)
         m = torch.nn.Conv3d(