[Dy2stat]Remove all comments of users code when dy2stat

[0x45f]

PR types

Bug fixes

PR changes

Others

Describe

动转静时，将函数中的注释行进行删除。
之前对下面的代码进行动转静转写时因为有函数体外的注释行，使用gast库进行func2ast转换时会导致出错，本PR之后将注释行（#开头的行）进行了删除，下面代码动转静不会出错。

    def forward(self, x):
        x = self.conv1(x)
        x = F.relu(x)
        x = self.max_pool1(x)
        x = self.max_pool2(x)
        # import pdb; pdb.set_trace()
        #x = paddle.flatten(x, start_axis=1,stop_axis=-1)
#         x = paddle.flatten(x, start_axis=1,stop_axis=-1)
        x = self.flatten(x)
        # x = self.linear1(x)
        return x

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[Aurelius84]

LGTM